I am skeptical about games where you can supposedly make cryptocurrency, and even without investments. Perhaps some amount of money can be earned, it will be so little that it is not worth the time spent. If you know games that are really good at playing, you can get good money, then tell me. I will be really interested to get acquainted.
Most of the game giving away crpyptocurrency to make the game popular, some kind of marketing I'd say and most of them as you stated not worth the time.
However I always consider the cryptocurrency reward only as a gimmick but not a really useless gimmick I mean, you know adding crypto as a bonus will add some of fun.