How many players that have been stashed for 3+ years have come to the league and made a difference?
If they are not good enough to come make a difference when drafted, it's not likely that they will get good enough to make it worth a buyout of the contract a few years later.
Turkoglu. Dino Radja, Sarunas Marciulionis, Toni Kukoc, Marc Gasol, Sabonis, Stojaković, Petrovic