Because chains such as Weatherspoons probabably differ in quality from place to place.
I've been to Wetherspoons in Exeter, Cardiff, Bath, Loughborough and 2 in Bristol and to be honest, I'd say that the food itself has been pretty much exactly the same in each place. But the prices can differ - I found Bristol prices to be 50p-£1 more than Exeter prices (e.g. for the Club specials), and even within Bristol itself, the one in the city centre was £1 more for the same meal offer than the one just a mile up the road!
Obviously the amenities can differ as well - the ones in the cities are smaller, less family oriented and have no gardens/play areas for the children, but outside the cities they may have gardens and larger family sections - so I'd say the prices and the atmosphere would be more of a concern than the food itself if trying to decide which Wetherspoons to visit.
