Because it's easy, I have a permanent, indisputable record , I don't like having to get or keep track of receipts, I do not have to meet with anyone, and I'm protected against fraud by the landlord or their staff.
So is cash with a receipt, I have permanent, indisputable record also and I am just as well protected against fraud!
I'm not saying that bank transfers are not good, I'm saying that there is no downside to cash (apart from your paranoia of "having to meet people"!) and that bank payments are not the only way rent "should" be paid.