I think this is a good move for Microsoft
In a larger organization, say 5000 employees, adding a single Power App to the tenant would up the annual bill by $300,000. Zero people are going to go to their management and say "could we please spend an extra $300,000 this year to try it out and see if Power Apps are any good?" This eliminates that hurdle.
Now, I'm not sure Power Apps are actually any good; Microsoft's programmers are mediocre at best, and their management is all about the next new thing instead of high quality and customer satisfaction. But this move does make it possible for people to try out the new thing, whether it plays out in their favor or not.