It's not just one type of criminal after your login details. Different people want your password for different reasons, and most of them don't even need to be skilled hackers to get it.
Some hackers specifically target passwords to break into accounts directly, steal money, or access sensitive personal information they can sell or misuse.
Others don't hack anything themselves. They simply buy and sell leaked password databases in bulk, treating your stolen credentials like a product to trade.
Then there are automated bots that don't target you personally. They run leaked passwords against thousands of websites automatically, hoping one of your accounts uses the same login.