This is what killed me when I started swapping Alkalines for NiMH in the 00s. Every single charger sold in stores only charged in pairs, and because even then USB was creating a 5V world most things that needed batteries used 3 of them.

Even the charger that Panasonic sold with the Eneloops requires matched pairs.

The other issue being that NiMH seems to top out at AA size. Finding C or D sized rechargeables is basically impossible.