Basically this. jQuery is one of those things that's almost literally bloat: it adds nothing that your browser can't already do, it just wraps around it. You absolutely do not need to use it.
However it saves on development time. It's effectively a bunch of boilerplate code that you don't have to deal with. It's one of those things that if you were to decide not to use it, you're likely to end up rewriting a chunk of it by the time you're done anyway, so you might as well go ahead and use it from the get-go and save yourself some time.
(Which isn't to say you should always use it. I've written pages where the amount of dynamic code was small enough that using jQuery would make absolutely no sense. But the larger your project gets, the more sense it makes to use frameworks like jQuery.)