I want to like RetailMeNot but every time I try it, I very seldom come across functioning coupon codes. I don't understand what incentivizes people to submit bogus codes.

The codes are probably legit. There's just no incentive for anyone to clean up dead codes nor submit fresh ones except for the coupon providers themselves who might see retailmenot as a marketing angle, which seems to be very few.

Except they often come with “added today”, “verified today” BS.

Just like travel sites where you can book some remote roadside run of the mill in Wyoming for mid week, winter next year, and be told “14 people have booked this hotel today, hurry”.

No, they haven’t. Or certainly not for that date.

Perhaps they are expired codes, or if it's a link (and not something to copy-and-paste) — affiliate marketing.

I think nowadays some codes may even be limited in usage precisely because of such communities. they don't want millions to use a good deal with no payoff, so they limit certain codes to X000 and they die quickly. The library paradox.

It feels like it has been ruined by greed and grift like RottenTomatoes and generally everything on the internet.

They inject their affiliate code just like Honey does. Why do you think they open a new tab that loads the retailer's site when you click to show the coupon code?