many years ago when Chime by Orbital charted I remember they appeared on top of the pops and deliberately stood on the stage with their equipment set up but unplugged and their arms folded and unsmiling (showing that they really did not want or even need to be there).
another reason though is that the UK councils and cops have worked out that events what run after midnight cost more in NHS and policing costs than they bring in via taxes, and create noise/crowd/traffic issues, so they are only licensed in socially deprived areas where there aren’t other businesses to bring in the tax.
Add to this the rise in mephedrone use and the merging of townie and EDM scenes and they are actively restricting late night events / discos – whereas it is way easier to get a traditional pop / guitar music based daytime gig which stops at 23:00 or midnight licensed. So for those EDM artists who still want to try and make music a main career they are trying to reinvent themselves as performers.
I’ve seen this happen a lot in my town, also that there is now only two clubs what will play any kind of EDM so you get nights with odd mixtures of genres. I was joking with a friend at ICR-FM that it was like the 1980s again where “only blacks and gay people were supposed to dance in clubs”.