who uses cash nowadays

Cash exists for a reason such as in the case of power outages, most payment systems are down in that type of scenario, since those are reliant on electricity so cash is a back up.

No shop accepts them. ATMs give out 50 euro notes

Will electronic stores accept either 100 or 200€ bills when purchasing an iPhone for 1500€ upon paying in cash? Also, can you pay only with 200€ (x30) only in physical currency when purchasing a 8K TV that may be 6000€.