But they only time I save a number is if the person has really good Pokemon and wants to battle in the future. For example the Fire Breather with 2 Magmars. I saved him because Magmar gives out decent exp. Also, not to mention the people that give out free items. I just got a free Leaf Stone a couple days ago.
If there were an option to delete contacts (which there should be, and I'm angry that there isn't.), I would definitely use it like no tomorrow. And I agree, I hate when NPC's say the same thing over and over again as it make the game 'less real' in a sense, and it reminds you that you are merely playing a video game. ):
I never added people on their Pokemon, I just added people on their names and what their sprite is or status, aha I'm so shallow. XD;