I get that this doesn't scale though - a lot of features are just "done" at some point and keeping one or more people whose sole job is to maintain this may lead to them bolting on features just to stay relevant / stop being bored. But big tech can easily afford to keep people like that on.
(I mean they keep (kept?) tons of middle management on, who knows what they even do? Not emailing right now that's for sure am I right?)
I work at a company with a few thousand employees in the Netherlands, and have been moved around a few teams in the last 7 years (not by choice, the team is nuked and I'm shuffled off elsewhere).
Technically, the product is supposed to have a "handover" to another team who can do the maintenance. What happens in practice is the person who worked on it gets saddled with maintaining it forever along with taking up the responsibilities of the newer work that comes along their way.
I've accumulated a string of such projects, including one that's used extensively by a few large companies, and the only person maintaining it is drumroll ... me, in whatever time I can spare for it.