"Due to many requests, the submission deadline has been extended" is this real? following different CS conferences I see the following phrase very often:


  Due to many requests, the submission deadline has been extended.


Or something similar to this. 

I won't overestimate if I said 80% of the conferences (I have followed) have this attitude. This brings me to the question of whether this is true or people (conference organisers) admit a lie when say this. Why does this attitude exit in CS conferences? Do other fields experience the same thing?
Warning: personal opinion.

I view conferences that regularly shift submission deadlines as a little suspect. You're right that this happens in CS conferences, and it soon becomes pointless because everyone expects the extension ("Nobody expects the extension!!"). But your estimate of 80% is rather off. Almost none of the (many) conferences I submit to have deadline extensions for submission of the full paper. 

And don't underestimate the level of pleading that goes on. People will always ask for an extension if they have even a smidgen of hope that the pleading will work. It's only when a conference takes a firm stand for many years that people stop asking.