The main channels have given up the fight. ITV late night is as stated, phone in quiz shows, a method of getting money from the cost of the calls from the consumer. Reality shows where the punter also has to phone in are also big business, big bucks to the TV stations and phone companies.
Who Wants To Be A Millionaire, like all quiz shows, has low overheads and they even improve that by getting people to phone in to win ?1k when the contestant doesn't want to answer the question.
TV shows are now sponsored so you have to put up with those bloody irritating snippets before & after commercials.
Both channels have increased their soaps, cheaper to produce than other programmes, so that Corrie & E.E's seem to be on every bloody night.
I don't look back with rose coloured glasses as there wasn't a golden age when Minder, Fawlty Towers, The Sweenie, Steptoe & Son etc were all on at the same time (apart from now on cable) but there was always something on that you wanted to watch most nights of the week. Now you are hard pressed to find one programme you make a point to watch or record a week. For me, apart from Life on Mars, QI & New Tricks there has been nothing home grown worth watching for months, thank God for cable.