All these independents which are worse than Costa....it beggars belief!
If you're visiting/travelling, you don't have the luxury of local knowledge and trial & error. You have probably one opportunity for a coffee. Are you going to take a risk on poor coffee, nowhere to sit, stale cake, and rancid toilets, or are you going to go somewhere where you know you'll get a consistent experience (even if it's not perfect)?
The whole ethos of the chains, whether Costa, McDonalds, KFC, Starbucks, Wetherspoons, etc etc is the consistency and standardisation - that's why they're successful.
Just come back from a week in Bath. We found a lovely little cafe for lunch. Went in, sat down at a cramped tiny table, ordered, paid by cash (didn't accept cards) etc. Then when we asked for the WIFI code, they said, oh sorry, it's not working! Tried to go to the loo to find it was down a narrow corridor and up some stairs so inaccessible to my MIL! The whole "experience" is often lacking. The next day, we just went to McDonalds instead, meal not as good, but working WIFI, accessible toilets, and far quicker service.