Although laptop purchases are popular with college entry, some students at my school choose to bring their Desktops from home. I for one cannot stand using a congested, underpowered laptop.
Here at Worcester Polytechnic Institute in MA, there are many computer labs and they are always full. Why? Because a lot of students like the option of using a desktop computer over a laptop. Also, if I have my desktop set up off-campus, it's nice to have an option to use computers while on-campus. Additionally, the school maintains expensive software that would otherwise be difficult to acquire and maintain on a personal computer, such as National Instrument software like Multisim, PSPICE, CAD (AutoCAD, SolidWorks,PRO-E), Adobe CS, MATLAB, Maple, Mathcad, Mathematica, and a plethora of other educational engineering software.
I don't know about non-technical schools, but here at a tech school, PC labs are running strong and will continue that way for years to come.