The subscription model is especially for those who might not want to own the product forever; like those who want to use it for a couple of months to a year and quit. Since its launch, I have seen the majority of new subscriptions shift from the monthly to the annual. And now, as of the start of this year, I have seen a bump in the lifetime subscriptions.

The other great thing about subscriptions is that you, the user, get lifetime updates/support/upgrades.