I disagree with the "forces them". You shouldn't post a non-answer (that what we call, beside others, a comment posted as an answer) if you don't have enough reputation yet. This is meant as a protection mechanism to avoid spam or other unwanted comments. However, I see how this can be frustrating. Having a rep limit on posting answers would not make sense, because then you would be forced to get some rep by asking questions only, and there are a lot good people which post excellent answers but don't need to ask questions.
Getting the required 50 rep should not be that difficult. That's 5 answer up-votes or 10 question up-votes. You should not have a problem getting these by posting 1-2 good answers. See this as a form of qualification test. This site (like all SE sites) simply targets at a higher quality than forums where everyone can usually post everywhere immediately. You should know that all reputation limits are given to us by the SE admins and we TeX.SE moderators don't have any direct influence on them. They are AFAIK the same on all sites, besides private-beta sites which have lower limits in order to seed the site with posts and tags etc.
Note that you can always comment on your own questions and their answers. The 50 rep limit is only for commenting everywhere. Also if you have 200 rep (from where on you are taken as a full site member) or more on any stackexchange site you will get a bonus of 100 rep for every other stackexchange site account you create (however just once in total), so you will be able to comment there immediately. You basically just have to prove once that you have learned how SE sites work.