How can I put this even more simply?

PRS royalties are collected and distributed centrally and are payable in respect of airplay and live performance. Whoever holds the publishing rights gets such payments direct from the PRS.

MCPS payments (mechanicals) are collected as a result of numbers pressed then sold when the producer has applied for and received a licence. CDs produced at a proper pressing plant from glass masters are rather less likely to escape this control than CD-Rs burnt on a computer and no licence obtained. No returns = no artists' royalties.

So it's not hard to work out who loses out in each instance.