First, I have idle accounts for brand protection. I really dislike being forced to participate in the handle registration gold rush to begin with. Now I’ll have to set aside a day every few months to log in to all of them. It’s not a huge deal, but it’s annoying.
Second, if idle email accounts become available for re-registration it might expose some users to account takeovers if they own accounts with email addresses they’ve forgotten about. And, what about people forwarding from accounts they never log into directly? I wouldn’t consider those inactive. Does Google?