Now that I know how basic Stack Exchange sites work, why not grant me basic privileges on all sites?
It's like having my hands tied behind my back on each new Stack Exchange site I visit. In fact, this question right here serves two purposes, 1) to find out this answer, and 2) to grant my privileges on Meta Stack Overflow. Only one of these purpose is "true" and the other has an ulterior motive, just the kind of fakeness I would presume you would want to avoid.
And now that I'm thinking about reputation points, I'm worried that this isn't a question that will answer well. Again, not something you really want your "true" visitors to be feeling.
So, now I'll make this into a feature request: Once you grant me the ability to vote and comment on one site, give it to me everywhere. The experienced of you will not share my pain.