Hi,
Zwift would expand its user base faster if it was possible to buy a subscription for somebody else who does not have a credit card.
Many people don’t have credit cards - for instance, in my country (Poland) debit cards are prevalent, and many people do not see a need to get a credit card (especially that credit card debt beyond the grace period is seen as a pest). We use electronic wire transfer, and we haven’t seen paper checks in about 25 years, so it’s not like we’re backward and will catch up 
You can use someone’s card, but that limits you to people who trust you enough to give you the details and then count on you to cancel the subscription when requested. Or people who you trust enough to give them your Zwift login credentials (and who trust you enough to count on you to cancel the subscription when requested).
However, I would not feel comfortable with this arrangement with someone who is not a family member or a very very very close friend at the least.
I have been approached by a stranger in an internet forum I post in about Zwift, and this got me thinking about an option like this. This could be implemented by selling promo codes, for instance.
Please vote this up. Thank you.