I think and believe that there was someone and thought if they should sell it as subscription or as a package.
The reason why subscription won, was money. Its like every other gym membership out there.
One day, you will be able to sit in front of the numbers and you will not do the right thing. You will see exactly how many people paid for a year subscription and stopped using the app after 1-3 month.
And yo uwill have the number later on on who is having an on going subscription and who is not using it. And you won't stop the subscription for the customer.