I think the reason for buying a classic turntable is a combination of cost and sound quality. In terms of cost, a turntable such as a Lenco idler drive can still be bought on ebay for a few hundred dollars and with modifications and a DIY plinth compete with tables costing much more - check out the Audiogon thread.
In terms of quality, check out Albert Porter's system, which is high end by anyone's definition. He had a Walker Proscenium turntable, and replaced it with a Technics SP10. Here's what he posted on Audiogon on 11/23/08:
"I sold the Walker four months ago. I made this decision after comparing it long term against my Wenge Plinth, Technics SP10 MK2.
Photographs of it here at Audiogon: http://cgim.audiogon.com/i/vs/i/f/1193606055.jpg
And at Sound Fountain: http://www.soundfountain.com/amb/sp10plinth.html
I bought the MK2 in Feb 2007, 21 months ago.
During this period, about sixteen listeners joined me in the comparison with only one voting for the Walker."
Also on 11/23/08, he posted after listening to Mike Lavigne's system, that:
"I actually preferred the Garrard [301] with Triplanar and Koetsu Rosewood Platinum to Mike's Rockport with Colibri."
Finally, on 11/30/08, he wrote:
"Although I've only recently posted my decision, testing has been ongoing for 21 months. Nine others who heard the comparison bought this plinth plus MK2 or MK3.
Each person put their completed Technics in place and compared with their reference turntable and arm.
This resulted in the sale of two Walkers (w/Black Diamond arms), a Kuzma Stabi XL with Air Line arm, a VPI TNT with 12" JM arm, a Basis with Graham arm and a Raven.
For this many people to agree on this change means it's an excellent combination."
What this says is the best of the classic turntables - Garrard 301 and 401, Technics SP10, etc. are at least in the same category as the best of the modern tables - Walker, Rockpot, Kuzma, Basis, etc., in the opinion of a number of experienced audiophiles. When you factor in the cost of a classic table against the cost of the modern SOTA tables this makes them at a minimum a very cost effective alternative.