That could be limiting if it was a requirement of a genre, sure. But jazz and electronica can both have vocals or not so that's not a restriction on either form of music.

Most of the electronic music I listen to is instrumental and it is still very varied.

Ohh yes that is indeed true :D

I should have said few vocals. I know jazz has vocals sometimes, but they are few and far between. It seems they are mostly a part of older jazz styles: dixieland and swing. It doesn't seem as if more modern styles have them, except for smooth jazz. Then again, just because it's less prevalent doesn't mean it can't be done.

I did not know that electronica could have vocals however. I don't recall hearing any with vocals, but my experience with it is quite limited.

A lot of electronica has vocals. Here's one great example: