Why not for all enquiries? If you book over the phone, you pay a booking fee. Why shouldn't the charges be transparent and not charged by stealth via customers' phone bills?
I suppose if people cared enough about it they'd vote with their wallets and fly with an airline that does that. Fact is that most use other criteria in choosing as the LCCs have shown us over the pat several years.
It's disappointing that BA have reacted to the change this way but, while we at FT will always debate these things to death and beyond, most customers won't even notice and I'm sure BA are well aware of that.