It would have helped MY peace of mind to know that Asking my first question, + waiting 20 minutes would be enough to get me the rep so that I can start Upvoting questions and answers!
If you have an account with +200 reputation anywhere in the Stack Exchange network, you will start on all new sites with +100 rep for a total of 101.
Beyond that, we encourage the truly new users to contribute a bit and give the community the opportunity to get to know them and vote on their posts .. before we give them voting permissions.
As for meta, it's tricky. I would like to allow new users to participate here but it's almost impossible to do so without risk, because metas are very low traffic and a malicious new user could cause a lot of damage by posting junk. Thus the 5 rep requirement to keep the bar as low as possible -- at toe level at least.
There is also the argument that participating on meta is a (very minor) privilege that you should earn by at least participating on the main site for a little while, so you have a basic level of familiarity with our sites and how they work. We get a significant number of brand new users who come into meta.so (which allows 1 rep participation) and start explaining how we're all doing it wrong, our entire system is broken, the sky is falling, etc etc. All the old timers just roll their eyes..