> Is there just too much content now?

I would guess this is the reason. Before there was unlimited content or ways to entertain yourself on a screen, having additional content on a disc would have been a marketing point to make people feel like they’re getting more for their money.

But now, I doubt even 1 in 1,000 people would respond to that, since there is always something else that can be instantly switched to watching or playing, so why go through the effort?