Currently it's not very obvious that a wallet is privkey-disabled or not. As far as I know, the only indicator in the GUI is a small "eye" icon placed at the lower right corner. So showing this column title would make this more obvious.
Also, I think hiding the column title only for privkey-disabled wallets breaks the harmonic looking of the wallet GUI.
By the way, I once heard that some scammers who once made use of the watch-only wallet feature provided by Bitcoin Core to take misleading screenshots, for example, to pretend as if they were OG miners who had participated Bitcoin mining in very early stage.