Here you go.

https://twitter.com/dabernathy89/status/1257350535440748547

Edit: Also, from my limited research, the repair cost w/out AppleCare+ (or regular AppleCare if they don't count it as accidental damage) is around $1,000.

Extra pressure on the LCD cover glass.

On my MBA there's a small metal lip around the lid and the LCD is recessed into that. Something thicker than the lip sitting on the glass would negate the relief the lip provides.

The webcam is behind the same pane of glass as the display. It's similar construction to a typical modern cell phone.

When the laptop is closed, the webcam lands around the bottom of the trackpad. There's a small gap between the screen and the lower lid, and the trackpad is recessed slightly, but not by much, and it doesn't have any "give". A bulky webcam cover will strike the trackpad and may shatter the glass of the display and/or the trackpad, especially if the laptop is closed quickly.

MacBook Pro screens have gotten cracked due to camera covers: https://www.macrumors.com/2020/07/10/apple-macbook-camera-co...

I had a basic post-it like bookmark sticker on my macbook pro camera for years. Over time the black coating on the bezels started wearing off where the sticker was placed. Not much of an issue though, as this was purely a cosmetic issue.

If the camera cover is too thick it's very easy to crack the display itself by closing the lid too quickly