When you make it harder to buy physical there will be less physical sales, of course. So many games only release digitally, don't have the full game on disc, are on a key-card, etc. And don't forget: The PS5 is an expensive piece of hardware and there is a cheaper digital variant of it. This is even more true with the Series S. All these things combined push you towards digital sales. I own a Series S myself because it was on sale for 199€ a few years ago and I never would've shelled out the money for a Series X or PS5 with disc drive.
I don't think anyone is arguing that physical sales are the majority or that digital isn't important or that the PS6 will crash and burn because of this decision. But physical is still important and when people have the choice they often buy physical. Also, many people who prefer physical media have probably partially or completely switched to playing on Nintendo consoles. And the last time I checked, those were selling pretty well...
