Yes, many students do.
However, some do volunteer or do minor research. At my school, to even be eligible for certain academic honors, you have to have a certain amount of volunteering hours as well. This isn't the norm I don't believe. I am writing a manuscript during the semester that doesn't take up too much time, but that is not the norm either. I would highly suggest NOT starting any type of research until you've taken a few tests to gauge how your studying methodology works. I tutor for a couple hrs a week for some extra spending cash as well but am probably dropping that in the future.
The volunteering commitment I have is nowhere near undergrad though. A couple hours on a Friday afternoon isn't going to sink your grades or personal life. A lot of it is medically related too. For example, as a clinically ignorant M1 it's kind of fun to take blood pressures or give flu shoots at things like health fairs or free clinics. I'm shooting for 50hrs/ school year only because we get a special distinction on our dean's letter if we do.
As others have said... board scores, LOR, rotations, and maybe class rank for some specialties is where its at. Research will help for some programs and specialties as well. I volunteer because I think it's a good thing to do and I get recognition in a LOR but it's very minor.