They aren't riders in the U.S. sense in any meaningful way because of sec. 54 of the Constitution Act 1867, which gives the government -- even a minority government -- the exclusive right to introduce (into the House of Commons per sec. 53) money bills:
It shall not be lawful for the House of Commons to adopt or pass any Vote, Resolution, Address, or Bill for the Appropriation of any Part of the Public Revenue, or of any Tax or Impost, to any Purpose that has not been first recommended to that House by Message of the Governor General in the Session in which such Vote, Resolution, Address, or Bill is proposed
That is, *first* recommended.
The rules of both houses of Parliament impose further restrictions on their members with respect to amendments.
Omnibus bills are a problem, certainly, but it is one fully under the control of successive governments and tolerated by the House of Commons (who would force an election in rejecting or heavily amending a money bill), even during the recent series of minorities and weak majorities.
The federal government further enjoys several powers to veto legislation that one house or even all of Parliament passes anyway, even when they control only a minority of seats in the House of Commons.
Omnibus bills are far from new, and the Canadian system was sufficiently weak that the Australian constitution (which granted similar exclusive rights over the introduction of money bills and the disposition of all bills) added section 55 to their equivalent Act:
Laws imposing taxation shall deal only with the imposition of taxation, and any provision therein dealing with any other matter shall be of no effect.
Laws imposing taxation, except laws imposing duties of customs or of excise, shall deal with one subject of taxation only; but laws imposing duties of customs shall deal with duties of customs only, and laws imposing duties of excise shall deal with duties of excise only.
Similar proposals have been debated in Canada for more than a century, however since Omnibus budget bills are under the control of the federal government, there has never been much headway made, and governments have tended to consolidate and split bills according to their own needs and pushback from the Parliamentary committees and agencies who review the bills. "Omninbussing" follows trends, and somewhat reflect the strength of party discipline across the whole of Parliament -- a relatively weak government is often the source of large and complicated money bills, while a government controlling both Houses and enjoying strong party discipline tends to produce more and slimmer bills.
Riders are a wholly different matter.
The U.S. system permits riders since the Executive can only exercise a Presidential veto. The only additional checks on riders -- arbitrary amendments made by majority vote in *either* house of Congress -- are the Origination Clause, bicameralism generally, and the rules of the House of Representative, which all serve to limit the damage any subset of Congress, particularly Senators, can impose on a budget bill. In practice, however, all sides compromise and allow arbitrary changes to be added by various factions on critical bills that the Executive cannot afford to veto, so the system is more a "balance" than a "check" on legislators. Successive House majorities have over *centuries* softened their stance on the exclusivity of their control over the budget process, by weakening their own interpretation of the Origination Clause, by compromising with Senators and House factions, and by continuing to present to the President bills that are difficult to veto. On the other hand, the Executive has adapted by lobbying individual members of Congress directly and aggressively, and various processes have evolved such that the Executive can effectively derail items in money bills that it objects to; most of those exploit the essentially permanent weak party discipline in Congress.
Finally, you wrote, "99% of the time, the regulations and laws enacted through such dirty tactics are things which would never be approved if they were voted on as single items". However, the standing committees in both the House of Commons and the Senate do in fact typically vote on each individual item; contentious matters are further voted on individually in Committees of the Whole rather than splitting the matters out into individual bills (which would require new Royal Recommendations). However, all these votes are won by a majority, and when a government's supporters dominate all of Parliament, they are practically foregone conclusions, as individual internal party factions' disagreements are typically dealt with in advance by MPs and Senators lobbying ministers directly or in caucus meetings.
Things that reasonably could be called "dirty" or at least highly partisan and essentially severable matters did find their way into money bills during several recent minority governments, and survived passing through a fractious Houses of Commons and even a Senate controlled by opponents. All parties agreed to compromise rather than to force an electoral contest over each (or any) such matter, although most of them passed essentially unchanged. Indeed, the motion of no confidence that triggered the 2006 federal election was not triggered by the a conflict over a particular piece of legislation, in spite of collapsed deals on compromises between the government and the opposition parties.
Finally, on the matter of riders and budgets, the Clark government collapsed in 1979 because he had not pleased enough of the various factions of the House of Commons. The formal mechanism was an amendment to a money bill that was insisted upon by a majority of the MPs present, and that amendment was simply a wrecker ("... that this House has lost confidence in the government") in part to avoid running into the Royal Recommendation rule that additionally prevented a potentially saving amendment proposed by a minor opposition party which would have required one in advance. The minor opposition party was, amusingly, obliterated in the 1980 election when the créditistes lost all five of their seats to Liberals. Had the Canadian federal system permitted riders in the U.S. sense, and the sense I believe you mean, the Clark government likely would have continued for perhaps another year, and would have faced a Liberal party led by someone other than Trudeau.