I think it's likely to be a product of internal incentives and how these create a culture. I would be prepared to wager than it's much easier to get a promotion by working on a new hot thing than on maintaining or improving an existing thing.

Scroll forward a couple of years and you have a reputation for just abandoning existing things rather than improving them, because people individually maximise their own career advancement by migrating off difficult maintenance and improvement projects on to "new hotness" projects only to abandon them again later for an "even newer hotness".

Small organizations have an immune system that rejects bullshit like that but as orgs grow they institutionalize and it becomes harder and harder for them not to succumb.