Because I pay cash and keep the bankers out of the transaction it costs me less and it costs the seller less. I negotiate this ahead of time. Most people in business would rather have cash in hand than wait on the bank and pay their fees.
In EU you could pay for all those things with a quick and free bank transfer for any amount, so you wouldn't even need to withdraw and travel with all that cash on you. There's no "bank fees", there's no "bankers" to keep out of the transaction, because they don't take any fee.
Other way around (in the Netherlands, which is the subject), bank transfers are free but depositing cash as a business costs money. Paying cash costs the seller more and holding it has a risk of robbery.
Cheaper than handling cash though.