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.
If they pay by transfer they can charge back, the bank might cancel for some credit reasons, might flag it as they want to verify first why it was made, and so on. Cash is problem free if you live in a low crime area.
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.
I'm always taking the wire transfer any day of the week. Nowadays, I generally straight up refuse payment in cash. Far too much of a hassle to handle. I think there is a major cultural divide between some parts of Europe and the USA on this subject which is partially due to how behind its time the USA banking system used to be.
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.