They're often cheaper on disc. Random sales here and there nearly always undercut the PSN price.

The real reason I've not bought many this gen was PS Plus. There's a lot of games I'd have been vaguely interested in picking up on a decent sale, only they've never been on one, and then went on PS Plus so now aren't worth buying at all.

Realistically the loss of physical discs means we need far more robust digital rights. The right to trade games to other accounts. The right to continue playing them if the store closes, loading games and licence keys from USB etc. That last one is going to need some thought to prevent abuse, but I think it's essential if we're going to live in a digital future. On PC that last one could be done by transferring licenses to another store maybe.