That is so Basic.
Why wouldn’t they? Never change something that’s dies all it needs to do.
I am a fan of innovation and new gadgets but not just for the sake of having something new.
Ordinarily I’d counter that with the price of replacement parts and the cost of labour for people skilled in system or OS maintenance for the era…
…but I should imagine you could trip over C64s (or their derivatives) in most tech fairs or car boot sales, and I’d imagine that most current gen software engineers got their start in BASIC, so yeah. Absolutely spot on call. It works.
POS and ordering systems are incredibly expensive nowadays as well. If the one your dad bought when he opened in the 80s still works for you, and you can reliably keep it that way, why not? Most small businesses, especially with the rising costs of business real estate, run on razor thin margins. Even shelling out a hundred or two for a software license can be rough.
There are c64 emulators, so as long as they don’t need some obscure hardware connection then they could continue using this system even without the hardware itself