Some people obviously care, but beyond that, I think it's an easy low hanging fruit when building them. There's lots of API's for it, the data is extremely regular, you get to show a graph and colorize some +/- and it has enough "bits" (symbol, name, price, delta) to look showy and interesting without being too complicated to actually design - the symbols even basically fixed width at 3-5ch.

People that make a percentage of their income from company stock?

I don't really want to be a stock owner, but the difference between paying my bills and doing more comes down to how people feel about the value of my companies stock.

Neurotic people with gambling addictions?

Might be because it's a reliable and stable source of data, so it's not hard to implement. And it's something which is updating often, so it makes sense to have it as some kind of noise on such a tool, even if you do not care much about.

BigTech employees often have 50%+ of their total comp paid in stock. Startup employees can be drastically more.

You get real twitchy about stock market movements around vesting time...

Maybe water cooler chit-chat.

bank employees who often get these kind of customized dashboards setup.