Hi,
Right, let's get some facts shown here.
1 - In a perfect world, we'd all be catered for, on TV, on all channels, with all of our favourite programming, and with/without signing/subtitles/no DOG's, etc, etc. Everyone would be happy. Everyone could chose whether they wanted or didn't watn subtitles, signing, etc.
But, this is not a perfect world, and so we all have to make do with what we've got. It's not the best solution, but there it is.
2 - Hard of Hearing (HOH), refers to people who may be deaf in one ear, partially deaf, or simply have some other audio impairment that means that simply turning up the volume on a show doesn't work for them. Medical issues like tinnitus (a permanent ringing or other annoying sound, that makes hearing very difficult) is one such condition that springs immediately to mind.
3 - In Britain there are approximately 66 million people living here. Of those 66 million, recent statistics from various deaf/HOH/disability charities state that there are roughly 8 million people who have some kind of sound or hearing problem. (This figure includes both adults and children!)

And about 1.5million of those original 8 million, use/prefer or require sign-language!
So, bearing in mind how little TV programming is actually signed on terrestrial and digital TV, that's about 1.5 million people that may like to watch TV, but for one reason or another can't, or find it difficult to do so! That's a lot of people in my book, and this is why there are more programmes and films being Signed on TV.
In all honesty, those of you (including myself) who don't need sign language, should be grateful that we can choose to see 99% of all other TV output, untainted. If you are deaf/HOH, and do require sign language, your choice of programming is very, very, VERY limited. Most of the TV channels don't sign programmes at all, and those channels that do, only do so late-at-night on older shows/films that have been on before. The BBC does a late-night strand of programmes that have recently been aired from the previous week, with sign language and/or on-screen subtitles, four nights a week, which is to try and improve the amount of programming available to deaf/HOH viewers!
However, for almost every other major show/movie, deaf and HOH audiences are restricted to subtitles (which aren't often very good, or very accurate via Teletext or Ceefax) or subtitles on DVD's.
Ultimately, if you are one part of the 99% of the population that doesn't need sign language, be grateful! At least you get to see most stuff on TV, when it's new, without any fuss!

The 1.5 million who can't, have to deal with just the odd programme or movie, once in a blue-moon!
Pooch