I can't be sure, but I don't think it used to be that way years ago.
However, I've taken a close look at my account. I recently received a paypal payment for 20p. Some plonker who's 200 miles away and doesn't understand 'collection only'. So I refunded him and told him I'd send the item for 0.20 + 2.95p&p.
The first thing I notice is that the payment of 20p didn't net me anything. No surprise there.
But then, to add insult to injury, if I understand the account properly, to do the refund they then docked me 20p, dammit.
OK, 20p is peanuts, but I still feel outraged.