Why can some contacts be added as favorites and other not?

[Android Central Question]

When I tap their name in contacts, then details in the drop down, some numbers I have the option to add as favorites and other don't.

Can anyone explain this? Is it a setting on their end or is my phone got a glitch?

 

[B. Diddy]

Welcome to Android Central! Which phone? Just to be certain -- you're in the Contacts app, right? You're not in the Phone app looking at the Recent Call History tab, right? If you're in the latter, then any number that called you who isn't saved to your own contacts can't be set as a favorite.