It just put unnecessary cost and headache on hospitality who had to spend alot of money on kitchens and "chefs" and then got closed down anyway after a few weeks at Christmas.
No one forced pubs to pretend to be restaurants. The vintners lobbied hard for the pubs that served food to be treated the same as restaurants which were shown to be lower risk. The government acquiesced and some pubs of their own volition installed kitchens to they could open as a restaurant. The blame for shutting them down quickly lays squarely on the publicans who were failing to implement basic distancing or stick to the rules and their customers, remember the scenes of people dancing on bars?