Why is it that so many middleweights from the early 90s are still fighting?

Nigel Benn, Steve Collins, Chris Eubank, Roy Jones Jr, James Toney - All of them are still active or are looking at returns: Benn vs Collins 3 has just been announced. James Toney has recently called out Roy Jones Jr for a rematch. Eubank has been in talks with Nigel Benn for a third fight. On top of these , Bernard Hopkins only retired late last year. Let me know if I've missed anyone else out. Why are so many from this specific era and division still looking at fighting? Are there any other eras or divisions that are still replicating fights from 25 - 30 years ago?