But AMD cards use less power with integer performance.
AMD is generally more popular among hobbyist miners, I think, because early on they had a performance advantage in Ethereum and hobbyists tend to follow each other like a herd because they have limited time to do experimentation and exploration (and this is not a criticism of them, they have day jobs and it takes a lot of effort to even get miners going, let alone optimize them across multiple parameters.)
[1]: https://motherboard.vice.com/en_us/article/59zdjq/an-idiots-...
If you are the manufacturer, why not let the customer take the risk? You are planning and spending years ahead, why gamble more than you need on cryptocurrency price?