Since my computer is 64bit, wouldn't it make more sense to have 64bit OS as
well?
Not necessarily.
The advantage of running a 64-bit version of Windows exist only if you
also run 64-bit applications under it. Bear in mind that there are
very few such applications available yet. If you are presently running
32-bit Windows, you don't have any 64-bit applications, so to achieve
any advantage, you not only have to replace Windows, but also your
applications, *if* (and that's a big "if") 64-bit versions exist.
Also note that you will need 64-bit drivers for all your hardware.
Those drivers may not all be available, especially if some of your
hardware is a few years old. So it's possible that you might also have
to replace things like your printer, scanner, etc.
So the answer to your question is that it's probably a poor idea
right now. That will undoubtedly change in a few years, but for now,
64-bit Windows mostly means extra trouble and expense for little or no
benefit.