Because use wears things out. My 20D is certainly not in the condition it was new. If the question was "Does anyone drive cars from the 80's anymore" then you'd be surprised not to get a "I still do" - a car from the 80's is not going to perfectly reliable simply because use has worn it out.
I somtimes carry my 20D in the back of my 1982 motorcycle... 

Just the other day i was doing a side by side ISO comparison with my friend's D80 and ISO3200 (ISO4000
not too keen on the 40D. 40D is a nice cam but the upgrades over the 20D are just not worth paying 1100E for it having the 20D working just fine and pleasing. At least for me.
