Anyone know why Handoff/Apple Watch doesn’t work on a reinstall?

So I was getting some bugginess on my install after the supplemental upgrade, so I decided to backup and nuke it. I make a new usb, load all my kexts and configs and everything, and install macOS. On finishing I realize the EFI partition is still there and it boots fine, so I just roll with it. Now, I notice that handoff and Apple Watch unlock won’t work after this reinstall. I’m planning to reinstall anyways, but I just wanted to ask why a new install using the same configs and kexts.