Here's a great laptop webcam comparison from Joanna Stern of the WSJ:
In our coronavirus-tainted world, we’re realizing that we depend a lot on our laptop webcams… and they’re not good. WSJ’s Joanna Stern compared the new MacBook Air to the Dell XPS 13, Google’s Pixelbook Go and Microsoft’s Surface Laptop 3.
www.wsj.com
I get that some people may not want the highest resolution for video calls! [Plus Zoom's default is only 720p anyways.] But I think they'd at least want decent lighting compensation and less noise, which the Apple laptop webcams could be better at (though they are much better than that on the Dell XPS).
One technological solution to improve both lighting compensation and noise would be to use a module consisting of a row of three 720p webcams (doesn't require any more thickness than a single 720p webcam), and combine their signals digitally. This would provide a higher dynamic range, and less noise, than one webcam alone. But it does increase cost and complexity.
As for resolution, it is possible to put a 1080p webcam in a laptop, e.g., that in the Pixelbook Go. At 13.5 mm, the overall thickness of the Pixelbook is less than the MBP's 15.6 mm. But of course it's the thickness of their lids that matters when it comes to fitting a camera, and I don't know how those compare.
According to this article, smaller bezels do create technological challenges for fitting higher-resolution cameras. However, miniaturization is possible—e.g., also according to this article, the front-facing 4k camera in the iPhone 11 Pro is small enough to fit into a laptop screen; so it may simply come down to cost:
Thinner isn’t always better for computers
onezero.medium.com