[robocat]

Aside: earned reputation seems to last forever.

I got to top 10% about ten years ago, mostly through basic questions and answers that you could easily do when StackOverflow started. I haven’t touched my account in years, and I am now in top 8% with about 5000 reputation, because old questions and answers keep getting upvotes.

I would think few people have much incentive to try and gain StackOverflow reputation, so what keeps StackOverflow going?

[listenallyall]

This isn't an aside, you identified the main point. You're entirely correct, all rep lasts forever, further, all the easiest "deposits" have long ago been mined. Early adopters like yourself answered basic, universal questions and earned thousands of points, some tens or hundred of thousands, for providing knowledge that was easy to find or that almost any programmer already knows.

2 things: earning points is exponentially more difficult today, you have to answer quite specific, detailed, niche questions -- and are rewarded with just one, or a a handful of points. Very unlikely you'll get hundreds of thousands.

> few people have much incentive to try and gain StackOverflow reputation

Totally correct. After 15 years, people have realized the points don't have any value. It was fun and cool for a while but at this point, who cares? Would you ever put your SO point balance on a resume? There's simply no benefit, and it's much harder to earn, so why waste your time?

[robocat]

StackOverflow is “open knowledge”, so I enjoyed adding to it as I helped many people in the world. I am not involved with open source. I was very careful to be correct and what I wrote was often unique knowledge, although it was often about browser quirks so what I wrote has mostly become outdated.

If I were employing a developer, and the developer linked their StackOverflow account, I would definitely judge the quality and quantity of questions and answers. “Farming” reputation to use as a reference requires a lot of skill and judgement.

There is only one person in the top 30 at place #15 that has been using SO less than a decade: https://stackexchange.com/leagues/1/alltime/stackoverflow

I know one of the top ten, and I would employ them (although I would be surprised if they choose to work with me).

The question of activity can be answered because SO publishes data. For example, the StackOverflow user database can be queried using https://data.stackexchange.com/stackoverflow/query/new for LastEditDate, as a proxy for user activity. Or grab the raw database and work out activity over time?

(edits)

[pasc1878]

What keeps it going is adverts to the low rep users who can't turn them off.

They tend to use google to search and then find the SO answer. Yes trhey tend to be beginners and ask the same questions as the beginners 10 years ago. Thus the rep from your old question keeps growing.