Ask HN: Why does OpenAI's API require purchasing "credits" now?

Title says it all. I received an email explaining that all API fees must now be paid with “credits” which must be purchased in advance.

This is less convenient and also seems a little greedy to me? I’m willing to give them the benefit of the doubt but I also noticed that these credits expire after a year which feels very “gift card adjacent”. I obviously doubt that I purchase credits and don’t use them for a whole year, but someone will and the only reason I can think of for that is to effectively get free money for some percentage of credits that expire.

I know other online services do this, but usually there is a way to automatically refill credits, and I don’t typically see any sort of expiration dates.

What gives? Just profit-minded business strategy or is there a specific reason they want to switch to this purchasing method?