Here's why:
Your patent only protects you in the country in which you register it, meaning that to retain control of your product you may need to file separately in each jurisdiction - Canada, USA, UK, etc. Also, it is a common misconception that a patent protects you from someone stealing your idea and using it commercially. This is not the case. What the patent does, is afford you legal standing so that when you happen to discover someone who has stolen your idea and used it commercially, you can subsequently sue them for compensation. Not only does this necessitate being proactive in researching possible violations on a continual basis, but should you discover an infringement, the subsequent process in the courts is generally much more expensive than the cost of the patent, and these costs must be considered in any cost/benefit analysis of a patent application. Having a patent without the resources or the means to enforce it is as good as not having the patent at all. Finally, your patent remains valid for a definite time period, after which time the intellectual property of the patent falls into the public domain. The idea here is to give an inventor a reasonable opportunity to recover development costs and make some money on a commercial implementation of the patent material, but to eventually let the intellectual property into the public domain in order to further the sum body of knowledge and technological development. By contrast, if the details of your invention can be obscured in a manner that prevents reverse-engineering, retaining your invention in the form of a trade-secret is often a better choice, as the secret lasts indefinitely - providing you with the opportunity to profit from the invention for as long as you can successfully keep the details out of the public domain.
