@jeder Given the proportions the first class vs second class in regional trains where they actually have the first class, the difference would be barely noticeable, but you provide a nice option for people willing to spend a few euros more. And to be honest, it's not just a convenience – for some it might be crucial to be able to work on a train, for example, and with the first class in regional trains, they can pay to have it for the whole journey.
I mean, I'm cheap, but it's not always possible to guarantee yourself the option to work with a race to the seat. It might work in Szczecin on the Stadttore-Linie, but not when you enter a busy RE in Hannover.
@jeder a fun thing in Britain: whether a train legally has first class depends on whether it is described in the timetable as having first class or not.
If a train turns up with a first class section, but the timetable says that it's a "standard class only" train, those seats are not actually first class seats any more