Part of the reason is actually advertising. Yes, they REALLY want you to remember what channel you're on. Another part is to keep those who record TV from getting a pristine copy of the show or movie. It's intentionally irritating so those who do record are more inclined to go and purchase the DVD rather than record.
why do they insist on displaying channel logo as though we did not know what which channel we are on ?and so aggravating when i am watching film
There IS something we could do about it, provided enough of us get together. We select a channel which has a particularly intrusive logo. (Maybe 'Dave' which now adds a line 'Also on HD' which only succeeeds in covering the characters' faces even more) We then select one particular advertiser and write to them saying that our 10,000 members and their families will not purchase their products until they stop advertising on 'Dave' or until 'Dave' removes the current addition to its logo.
We could then target other channels until eventually only those which don't display a constant logo will escape our purchasing ban.
This is the first time I've been on 'twitter'
Is there any way of bringing this to more people's attention?
No problem at all - provided it doesn't interfere with my enjoyment. I note the BBC does not have to clutter up their screens with 'advertising' as you call it. When 'TalkSport' asked for listeners to phone in saying if they WANTED to be contantly reminded what channel they were watching, NOT ONE of their millions of listeners did so. In any case, I always thought the commercial channels got their money from advertisers. So how can it help advertisers if viewers automatically choose a 'non-logo' channel wherever possible?