While I don't "force" myself to do everything the opposite of the "right-handed" way of doing things, this world IS setup for right-handed people. Any left-handed person who's ever used a knife or a pair of scissors knows this. We are, in essence, "forced" to use our off-hands for dexterous manipulations. This isn't conjecture. This is a plain unfortunate fact.
Yes, knives have a handedness to them. A great majority of kitchen knives, for example, are ground with an edge favouring the right hand. Pocket knives are notorious for having handedness applied to them simply by making their operation right-handed. True that there are some ambidextrous folders but they aren't the norm or are only so in the most general sense. If there were a company to suddenly spring into existence making knives exclusively for lefties, they'd have a customer for life. But, as others have said, we are a small minority and have to kowtow to the right-handed majority we live with.
How freakin' hard is it, though, to get companies, regular find-in-an-hardware-store companies, to run a batch of rulers and squares and tape measures in mirrored notation? If you aren't left-handed, you might not ever think that would be an issue...but it is.