Transferring a physical ticket isn’t that useful as you have to travel to the person you want to give the pass to, anti-passback is sufficient for the only real use case. Same reason it isn’t a problem with Oyster capping (and why contactless capping is tied to the DAN rather than the PAN).Most paper (usually barcoded these days) bus company day and weekly tickets are transferrable - either it's allowed explicitly or there's no effort put into preventing it so it's de-facto allowed. The one thing they want to prevent is passback, i.e. two people using the same ticket to board the same bus, which is easily enough done by only allowing a scan-in by that barcode on that journey once.
Very different story with e-tickets where a group of people could set up a WhatsApp group and share a ticket each morning.