The loss of some of the lower level Italian pro stage races could also be an issue, with races like the Settimana Lombarda, Giro di Calabria and the Brixia Tour disappearing (plus the Giro di Padania, but nobody misses that). There was once enough on the stage racing domestic calendar for Przemysław Niemiec to reach age 31 without ever going above Continental Pro.
There's always been a lot of one-dayers on that calendar - hence Murilo Fischer's crazy 2005 - but there used to be a decent number of stage races too. Paradoxically I think the paucity of doping scandals has probably been a catalyst for that. The Coppa Italia used to be very keenly fought and the number of high profile riders coming off doping suspensions or aging out and riding in the domestic teams - di Luca, Sella, Riccò, Pellizotti, Scarponi, Simoni, Garzelli - meant these smaller races were keenly fought out. Look at the 2010 Italian pre-Giro season with the likes of Ceramica Flaminia, Androni Giocattoli, CarmioOro, Farnese Vini, Colnago-CSF and Acqua e Sapone all producing contenders to all of these races - they aren't being invited to the WT races of the time but they need Giro form for those who are invited, and they need Coppa Italia points for those that aren't, and so you got a lot of hard racing which helped develop stage racers, even if they might not have been fighting for the win, they were competing with or alongside these veteran stage racers at that Continental level.