Earlier quoted context omitted.
Some REWEs have, but not all. There's still some where I live that don't. (REWE eG is a cooperative, so it's all a bit more complicated)
Basically there is Rewe Dortmund (with stores across NRW) and Rewe anywhere else (including NRW). The latter requires credit card acceptance for all Rewe-branded stores. If a store does not have that, an email to Cologne usually changes it.
And members of both have reservations against MasterCard and VISA, due to what happened with Rossmann a few years ago (Rossmann sold cuban cigars, as punishment MasterCard, VISA and PayPal seized Rossmanns funds and suspended all payments), but as EC was also bought by MasterCard and merged with the Maestro brand, currently there's no option but to continue on.
Personally, as member of both the REWE eG and coop eG, I'd support a move away from CC to any national or EU based payment system as soon as possible.