Just Say so!

There are many things I don't get, and it seems never will... I shall provide examples: why is it people don't say NO when they know for a fact that they won't  or are u willing or can't do something ??? Instead, they no longer pick up the phone or write back. WTF is up with that? Some sort of shame? Not wanting to lose face ? Hellloooo? 

Another thing : don't say u understand, when clearly u are clueless or have no idea on what to do. Again, no shame in saying "sorry, explain, I did not get it"... 

Urgh.