The ex-Chelsea boss said that other Bianconeri forwards may feel intimidated by the presence of the team's all-time record scorer, and thus his summer exit may be beneficial.
"It is legitimate for Juve to think of a future without Del Piero," Vialli told Sky Sport Italia.
"Maybe his presence scares the other strikers, as they do not feel relaxed and able to give their best. Perhaps having such an important man on the bench means they cannot take full responsibility.
"Besides, as far as Del Piero is concerned, it is better to have your departure regretted than have people put up with you. It's best not to one day hear someone say, 'Oh, when are you going to retire?'"
Juventus president Andrea Agnelli previously revealed that Del Piero will not be offered a new deal when his current contract expires this summer.
The striker's recent good form has prompted a fan campaign to keep him at the club.