But why?

There's no reliable source of truth for your home network. Neither the local (m)DNS nor the IP addresses nor the MAC addresses hold any extrinsic meaning. You could certainly run the standard ACME challenges, but neither success nor failure would carry much weight.

And then the devices themselves have no way of knowing your hub/router/AP is legitimate. You'd have to have some way of getting the CA certificate on to them that couldn't be easily spoofed.

EDIT: There is a draft for a new ACME challenge called dns-persist-01, which mentions IoT, but I'm not really sure how it helps that use case exactly: https://datatracker.ietf.org/doc/html/draft-ietf-acme-dns-pe...