Your motherboard already has a unique identifier, as does your CPU, your GPU, and I believe your RAM too. It's how their licensing system can tell when your existing Windows install has been transferred to another set of hardware You can overwrite data on your motherboard, but it's like 0.0001% of users who'd do that, so Microsoft doesn't care.

Now, it's possible there are errors in what I'm saying, I'm not an expert. But.

TPM allows Windows to make sure it's still on the exact same machine it was on before, for sure. No trickery. So if you lock your drive with Bitlocker using TPM, it's not possible to just clone your drive and try to unlock in another machine. Any data theft requires the user to have possession of the exact machine you configured it on, in addition to your Windows/Microsoft password. And if someone does something funky with your motherboard firmware, you can't unlock the drive either, because it's no longer the same trusted one. At the same time, a legitimate firmware update from the manufacturer can screw things up too if they're negligent about it. I believe Bitlocker has recovery keys for occasions such as this.

It's also a sort of a secure key storage I believe, so things like Windows Hello facial recognition use it (Apple similarly uses T2 for touch ID on modern macs, but since touch ID came before T2, I'm not sure what they used before).

TL;DR: It has security features, some of them allow for comfort features, some for stuff you don't need too much as a regular joe, but Microsoft is enforcing better security defaults like this because there are ridiculously obscure threats out there and they don't want to be known as "the operating system that gets the most viruses" anymore.