Some of them cut corners / do awful work.

Years ago my sister in law wanted an extra socket to power a washing machine.

She wouldnt let me do it and €œgot an electrician in€�

He put in a 13A trailing socket on a bit of flex (I think it had a 13A plug on the other end, dont remember).

It was just loose inside the cupboard.

I was appalled but said nothing.

Prior to that she had a cooker connection unit complete with 13A socket fitted.

The electric Board / company said you couldnt get flush mounted any more, only surface mount.

I personally think tap flexible connectors are a tool of the devil. But of course the trade love them.