Sure, it happened to me, I even have one or two buyers who keep buying my gig since a long time but never leave reviews. I don’t think you’ll find many people if any who have been here for a couple of months and still have a 100% review rate.
Sometimes, you’ll see people having things like “778 reviews, 1045 gigs sold” or such in their profile or on their gig, or posting it here when they post about their experiences, q. e. d.
Of course I appreciate reviews very much but if a buyer doesn’t want to leave one for whatever reason, that’s okay. As long as I get paid for my time, all is well.
Just do your best and if your best is good enough, you’ll eventually get reviews, most probably not every time - some buyers simply don’t want to review for the one or other reason (see the forum thread by a buyer who contacted support to delete a review he thought would not be visible publicly, for instance) - but often enough.