IMO it is because BIP352 is in reality an alternative to BIP32 (HD) and that meansthat you have to compatibilize two key management strategies, scriptPubKey detection, labeling systems, indexing/indexers. Backups are also different from HD wallets. Also, other concepts like read-only wallets are not compatible/possible.

This introduces a lot of friction. Moreover, many libraries don't support what it is needed to implement it. For example, NBitcoin doesn't know how to sign a non-tweaked key. So, it is not sooo simple.

Anyway, I think it worths the effort.