"More places to eat, drink and shop" doesn't strike me as the primary purposes of a station.
I agree, they aren't the primary purposes of a station but I don't mind as long as the design of them respects that fact. The main entrance of Manchester Piccadilly looks like you are entering a shopping centre, not a railway station, and in my mind is therefore an example of station retail done wrong.
See this photo (not mine) for an example of how shops can redesign themselves to be more in-keeping with an area (ignore the big white sign in the window, which isn't). Of course, that Spar shop in Carmarthen isn't in a railway station, nor is the style likely to be in-keeping with many stations, but I think it suggests what should be possible.
Don't Network Rail make money by providing outlets to rent out.
I believe they do, which is probably the main reason I'm not completely opposed to the idea of putting retail units in stations. It doesn't help however that Network Rail also charge for toilets at the stations they manage, surely the rent from the retail units can pay for the upkeep of the toilets. Don't most cafes outside stations have customer toilets at no extra charge? In a station like Kings Cross or Paddington, there are several eating/drinking establishments but you have to pay to use a Network Rail toilet! Even if they didn't have retail units, I'd be strongly opposed to charging for toilets.
Stations are aping airports
Do airports charge for the use of toilets?