The people answering "because PC has more sales" haven't looked at console sales in years so they don't know that times have changed since mid-PS4/XBO gen. Literally every month there's a new run of sales on console storefronts. So that's not the real answer.
The real answer (that actually only matters for PS and Nintendo), which is: Where would their digital games go if they left the console business?
They're against digital because they don't trust these companies to do the right thing in regards to their libraries and licenses.
However, the real problem here is the volatility of the console business, not physical vs digital or the out of touch 'sales' answer. Steam will arguably live on even after everyone here dies of old age. All it takes is one or two bad generations for Nintendo and Sony to leave and you're left holding onto a digital library you potentially can't access.
That's their problem.
Now what the physical owners don't understand is that they've already lost this war. Quite a few discs this gen are just day 1 download queue coasters that people will convince themselves is a real copy of the game on disc, and not just a key with half of the necessary data/broken game on it with the other half being in that initial huge patch.