It is easy to see why too tbf, it just makes gaming super accessible, and with some genuinely compelling exclusive titles it's so easy to subscribe for a month or two. I played through the entirety of Monster Hunter Stories via Apple Arcade with no regrets.
I understand your point, but I don't think Puyo Puyo is a strong enough incentive to subscribe to Apple Arcade, considering it's still considerably niche in the US. Making it an exclusive game might not be beneficial for it.
I'd argue it's a fantastic title for the platform as an easy to pick up kinda game, but I do agree that it being exclusive doesn't really offer much pull alone. In my mind I don't think any single game has that kind of pull for Apple, but the combination of the smaller titles they have do a good job in building up to a larger package.