sogood said:What's the advantage of dropping out of a major tour for the individual rider? I'd think that most of them would have wanted to complete the race or why enter it in the first place?
No, most riders are interested in stage wins, rather than riding an entire GT just to be pack fodder.
Many riders do this. Cipollini regularly rode only the first half of GTs (especially the TdF), riding to win the sprint finishes and then pulling out before the mountains. The TdF points jersey was not of interest to his Italian sponsors.
Cunego (the first name to come to mind) actually entered the Vuelta only to 'refine' his form in preparation for the Worlds. A number of riders like to race in the GTs to prepare for a more important (for them) objective that they may have later in the year. He discussed his pullout from the Vuelta with the Italian national team coach, got the green light, and left the race.
The solution would have to make it more important to complete GTs in terms of Pro Tour points or something of that type, although it has yet to work (and the jury is still out on whether we will have a Pro Tour for much longer, LOL).