In PVP, I buy them. For PvE, simply change it in some ways. Change the Pet Battle Dailys in two ways.
1. Always make them start with the same pet. I'm pretty sure that I'm not the only one that forfeit games to get the game I want to. (nowdays tho, it usally don't make that big diffrence anymore, but I know how frustrating it was when you only had 5-6 lvl 25's to fight with)
2. Always make your first ability to hit (in PvE, not PvP). Same thing here, who don't forfeit a really bad start when you miss with a 5 round cooldowner? Why fight for 3 minutes when chances to lose are 90%? When you can forfeit, and go again, and 90% win instead?
If not these changes, then get rid of the Forfeit-button.