It is about speed. If someone offers 10k in cash and someone talk about wire transfer blahblah, sellers will always prefer the buyer just paying in cash.
I would not feel at ease walking around with 10k€
In fact I would find it extremely suspicious if someone told me it's their preferred method to get paid. I would totally expect a mugging.
I do myself all higher priced purchases in cash, even go to the bank and withdraw the money to go to the shop next door. For the same reason I use a VPN. My provider and my bank have no right know what I do or not do.