Ok, let me try and put it into perspective:
This is Texas. We're talking southwest humidity. If I sweat a good bit in the cold in Texas, the driest time of the year, just imagine me in the high 90's with brutal humidity. Even on days in the high 70's I'm usually already sweating after having just taken a shower and riding back across campus to where I park my bike at (close to my other classes). And with that in mind, remember that it can be 10 at night in the summers here and still be in the high 90's.
And when I say bike specific clothes, I guess I'm being a little misleading. I don't always wear padded shorts, and I'm rocking pedals with toe clips, so no special shoes or anything, but I'm often in a wool jersey and wearing tights if it's cold enough. I need to get some lightweight wool T's or jerseys, but for now I'll have to run with thin polyester stuff in the summer. Basically, it's just stuff I wouldn't want to wear to class. I understand this may work for others, but seriously, if I rode 7 miles and wore the same polyester gym shorts all day, people wouldn't want to be in the same room with me and would talk about me behind my back. I can shower 3 times a day, but 30 minutes of good riding in polyester and that stuff just gets funky on me. This is why I stick to wool whenever I can. Not everyone has this same problem with polyester.
So yes, I understand that wal-mart shorts and poly tees work for short rides for many of you and can wear the same stuff all day. This just isn't an option for me, unfortunately. Trust me, I'd LOVE to be a generally less sweaty person. I guess it's glandular...