Actually, in my entire ~10 years of having been a grad student and then researcher in theoretical physics, I didn't take out books from a library even once! I have yet to come across any material that is not available in electronic form (well, one very specialized book, which I did buy, cut off the spine, and ran through a ScanSnap)
I attended grad school 2003-2009. The first few years I routinely pulled hardcopy at the library. By ~2007 I was able to get everything electronically. Not so long ago, dead trees mattered.
