"There are a lot of people back home hurting." Is Frisk's simple answer. "I want to help them."

They themselves are more then part of the problem, yes, and Frisk hopes they know when to stop when they finally find that happy ending. But no matter what they've tried so far nothing has worked.

And so they repeat, over and over.

But it's a genuine answer and a deep wish of theirs. The Ringmaster herself doesn't have to do the saving, just point them in the right direction. Even if it takes a year, if it finally makes everyone happy then it's worth it.