I think "install as digital" while the disc retaining value as providing a game would / could still allow publishers to make money in the second hand market, maybe that option could be 10$-20$ for the initial buyer as the disc would come with a unique identifier (like it does now) and full price after that, or maybe it would be as simple as having it the same as the digital download all through out, first or second hand.
Currently, as it stands, once the disc is out there, publishers can make no extra money. But once you give people the option of going digital for the comfort of it (instant game switching, no worries of losing / damaging the disc, at the expense of second hand value), publishers could see continued income from these discs, and any extra income should be welcome. Especially with the disc making the transfer of digital data convenient for people with slow internet speeds, but still would like a digital library, this could be a viable option.
Also, if they want digital to prosper so much, they should make digital versions slightly cheaper (60$ disc, 55$ digital). But I guess publishers / platform holders have too much stake in retail, that they can't "afford" to do this.