This was the only method available of doing payments inside the app in a way that met their product requirements.
It's fine to not like cryptocurrency; it's intellectually dishonest to accuse every project of crime without evidence.
I can recall specifically two kinds of crime with cryptocurrency: “pump and dump” pyramid schemes and money laundering, which is hiding particularly nasty crimes like human trafficking. I won’t deny these are terribly victimizing things (that would be truly advocating for the devil).
On the other hand, there are people who don’t enjoy the banking infrastructure that Americans have; people in nations without nearly the wealth of America. Now they have these open-source networks they can implement on their own terms. The people doing this research and making these offerings might be serving such customers, whether by practice or intention.
Crime is not “the perfectly sensible default assumption for cryptocurrency apps in 2023” unless the one making the assumption is naive to these perspectives. This is an (unconscious) anti-cryptocurrency bias by definition: https://en.m.wikipedia.org/wiki/Availability_heuristic.
