Play to earn is a charming idea. People work hard in games, it is said, and so they deserve to earn. Earning means becoming the owner of collectibles and then being able to sell those.
This also means players are asked to invest when they begin playing. For instance 'buy these monsters to breed them'.
Of course it's all in crypto. Tokens often also give access to governance, one can make proposals and vote in function of the number of tokens one owns.
The problem is that often the games are not that very fun to play. The real fun seems to be to earn crypto, and the actual game play is more like grinding.
In low income countries a game such as Axie Infinity 
allows some to quit their day jobs and just play and earn that way.
Some would call this 'bullshit jobs' where you do a pretty boring and senseless task in order to earn an income. It would be nice to see games which have interesting content and gameplay apply 'play to earn', taking into account the ecological consequences of various blockchains. Of even have games which are educational or have some societal benefit apply these ideas.