Basically, a website can block you or treat you suspiciously based on whether or not this “feature” says that your computer or browser is approved and unmodified.
This can become a problem as more sites adopt this. You can be using a 2 year old device and suddenly your bank stops working because your device no longer shows up as approved. It can be used to artificially enforce obsolescence. The fix would be to buy a new device.
You could be using Linux or a 3rd party browser and many websites will become unavailable to you because they can never show up as approved and unmodified. It basically breaks the open web.
While true, unfortunately the latest government spy bill is bipartisan. It will make end to end encryption for texts and chat illegal, using drug enforcement as the excuse.