I guess the main problem is the logistics and costs. With a Physical disc, you give them the disc, that is that.
Yea, probably. From a legal point of view, a licence is a licence no matter the transport media. For example, if I buy a retail copy of World of Goo from Tesco then I'm free to play it and then trade it in (and therefore transfer the licence). If I buy a digital copy then I should be allowed to transfer the licence to another person as well. I think this is what the EU ruling was trying to address.