Well, apart from Nick's suggestion that Brits prefer to spend most of their time looking backwards while wearing what may be described as spectacles with a slight rose tint

, live music in the UK has been in freefall since the 90s. Audiences have continually plummeted as the cost of getting to the venue, the cost of entry and the cost of drinks once inside have continually risen.
So often you can't get home the venue as public transport often doesn't exist by the time the gig finishes - assuming there's any public transport at all to get you there in the first place. Even in London the tube is closed by midnight. Yep, the main transport system in the country's capital city closes down at the same time most other countries nightlife is just getting started. If you want a drink you better have a friend who'll drive you home or deep pockets for the taxi ride. Back in 2009 I missed the last tube home - 23:30! It cost me £80 for a taxi.
Then you have decades of what can only really be called
propaganda regarding the worthlessness of art; how something's importance is measured purely in outright profit. This creates a society that stops caring about such things as music, that stops protecting or investing in such things as grass roots music and music venues. Again, the exact opposite of my experience in other European countries. And if someone from one of our European neighbours is thinking 'what's he on about, it's really bad here', I assure you that it's a whole different level of bad here.
In the 90s, cover bands were already becoming the only sort of band most venues were prepared to book. In my hometown of Manchester is was possible for an original band to play at a different venue every night of the week at the end of the 80s. In the 70s you could play a different venue every night for a month. By the middle of the 90s at least half of the venues I used to play at were gone, By the 2000s most had disappeared. All that was really left were pubs, where if you didn't play covers, you didn't play. Even if you did play, you were lucky if each musician got £10.
Then someone somewhere came up with the idea of having a tribute band rather than a band that just plays generic covers. Whether they intentionally realised it or not, they had come up with a way to attract an audience that could actually afford to buy a ticket - appeal to the nostalgia of middle class, middle aged people who have a disposable income. Play venues where you're unlikely to encounter drunken violence - another thing that put off so many people from venturing into cities - that are easily accessible by car, to see high quality musicians play your favourite music, usually watched from the comfort of a well-padded theatre chair.
In this country, if you're over 30 and still want to play popular music to an audience, there are only really two options (assuming you're not a working session musician) - play covers in a pub band or play covers in a tribute band. Rightly or wrongly most people assume the musicians in a pub band will be of a certain proficiency level that is not sufficient to play in a tribute band. Also, as has already been said, it's still possible to make money in a tribute band, and that attracts a lot of musicians, which means people putting together tribute bands have more potential players to choose from and that usually (but not always - boy, do I have some stories on that subject

) results in music played to a high quality.
It turns out Brits do still love well played music - unfortunately the only genre that seems to be able to sustain itself is the tribute scene.