Sony & MS aided in the decline of discs by making a disc drive an expensive add on and having every game need an online connection or day one update to fix bugs.
I'm sure they had a marketing plan of making $90 bucks off a $10 buck disc drive and then go "oh wow, look, only 30% of people spent an extra $100 bucks!"
It also enables them to effectively kill the used game market when you have to buy all games new through their store (or a code). You can’t even share a game with a friend, unless you share their whole account, which is way more friction.
They were also following consumer trends, digital purchases were already getting very popular before they introduced diskless versions of the consoles.
I'm sure they had a marketing plan of making $90 bucks off a $10 buck disc drive and then go "oh wow, look, only 30% of people spent an extra $100 bucks!"