Leading by that method, 90% of things implemented, can be erased, and explained with that sentence: do it manually, it isn't so hard to understand how.
It's simpler for everyone, to have this on auto. So, it is better, and when something is better, why not have it?
I could be physically prevented, or cut off from internet, to make payment, what then? To wait next week? There are lot of examples I can type here, why auto is better than manual, and this topic tells for itself.
It's not a question is it hard or not, when it can be automated.
If there is automatic recurring payment for premium account, why there isn't automatic payout option?