AC-DC, I have had the same thoughts - eg when tracking towards Lydd for a cross channel why talk to Lond Info - just listen out and get a picture of other traffic. Then I thought that if everyone else did the same then there would be no info at all on other traffic. So all in all best to put a call in - you never know when another aircraft hearing you may find it of use in knowing your position / altitude. Assumes of course you can get a word in edgeways. Always talk to LI whilst over the wet stuff for obvious reasons....
A2