If you're the kind of person who buys something considering resale value (I'm paying $40 for this game, but I expect to get $15-20 back when I resell it, so I'm really only paying $20-25), then you wait for a price drop on Steam equal to the amount of value you think you're losing by not having the ability to resell.
Yes, obviously if you buy something for $40 and sell it for $20, that's better than buying for $40 and letting it rot for $0. But when I bought Kane and Lynch 2 for $5 on Steam (it was $59.99/64.99 at Canadian retail at the time), I didn't expect to get any resale value back when I was done for the game and it was significantly cheaper than the game was on consoles even assuming a best-case scenario for resale.
On a day one level, most Steam games are $44.99 versus $59.99 on consoles. That's how Steam compensates for the loss of resale value for day one games. If that's not enough of a compensation, again, wait for a price drop.
This isn't meant to be a defence, just a factual statement about the fact that your buying habits should reflect the platform's value habits. Games that are worth less to you should be bought for less than games that are worth more to you. Games with no resale value may be worth less to you.
Also, this is not a digital/physical thing, it's a DRM thing. Many physical PC games have been un-resellable for years due to single-use key online activations. If you buy a Steamworks game today physically you can't resell it. It's not about physical/digital.