Why cant I request lives from ALL my facebook friends in candy crush?

[BILL]

Candy Crush does this so to prevent people from massively spamming invitations to other Facebook users about their game. People already complain about being flooded with game invites, and Candy Crush is already one of the most popular games people send/receive invites for over Facebook. Without this limitation, your 5-10 game invites when you log in to Facebook every day could balloon into 50-100. Those potential Candy Crush players who might only be slightly annoyed by the current level of game invites the receive could likely turn hostile after having to skim through an even greater number notifications.

Of course, the other likely reason is probably to limit your options and get you to pay up $$ so you can move on to the next level/stage.