[giantrobot]

Back in the stone ages Slashdot gave subscribers a comment bonus and an indication the user was a subscriber. An icon in the forums or some small benefit for "subscribing" goes a long way to get people to fork over a few dollars for something.

[PeterisP]

Lichess is a good example - their "subscription" gives a cool Patron icon wherever your user name is listed (usually the icon is just a circle that's filled if you're online), and that's it.