Because they are not very sophisticated in their knowledge of English. "Is there television in the room?" is how a native English speaker would put the question. But, I guess we'll just have to accept their version if we want to progress to the next level!
Sorry. To me "a television" means a TV receiver. "Television" without the article means the TV industry, or a TV signal or maybe a TV camera.
For example, if I say I'm watching "television" I mean the content came from the TV industry. I could be watching it on a phone, or on a computer, or on "a television."
Because in English a singular countable noun takes a determiner before it. For example you can't say "this is TV" you have to say "this is a TV".