Klobuchar frankly does not have a path forward to win the nomination. With centrists concerned about Sanders' lead, Klobuchar dropping out could help consolidate the field behind another moderate and block Sanders from the nomination.
Here's how Washington Post columnist Jennifer Rubin characterizes Amy Klobuchar's position in the race:
She is not the only candidate without a path to the nomination who should exit the race at this point, but she is in possession right now of a small share of the electorate that is compatible with moderate Democrats who can in fact win, if the field shrinks. And time is of the essence here, since early voting is underway in multiple Super Tuesday states.
Klobuchar's base think she is the right candidate for the job.