They're no longer energy competitive. I.e. the amount of power per compute exceeds what is available now.
It's like if your taxi company bought taxis that were more fuel efficient every year.
If a taxi company did that every year, they'd be losing a lot of money. Of course new cars and cards are cheaper to operate than old ones, but is that difference enough to offset buying a new one every one to three years?
Nvidia has plenty of time and money to adjust. They're already buying out upstart competitors to their throne.
It's not like the CUDA advantage is going anywhere overnight, either.
Also, if Nvidia invests in its users and in the infrastructure layouts, it gets to see upside no matter what happens.
Margins are typically not so razor thin that you cannot operate with technology from one generation ago. 15 vs 17 mpg is going to add up over time, but for a taxi company it's probably not a lethal situation to be in.