You might be right. Sorry. I should have said they haven't increased prices for existing dedicated servers since my direct experince is only there. Actually until about 3-4 years ago when the whole world went to shit, using a server for a year or two then upgrading to a better server for cheaper, was the norm. In that environment, you would naturally not have price increases.
I also don't think you're right that it never happened for the dedicated servers :) I'm only using Hetzner for dedicated servers, and found an email from 2022 where they mention price updates:
> Unfortunately, we are forced to increase the prices on these Server Auction models [...] old price 37.60 Euro -> 59.29 Euro, comes into effect 2022-03-03
Citing raising energy prices at that time.