Biden's policies, all of which Kamala would continue unchanged, are extremely unpopular. She would continue gifting bombs to Israel to commit genocide with, do nothing about housing, medical care, reproductive or trans rights, policing...

Giving people time to realize she's just going to be more of the same would probably hurt more than help. Especially in regards to Palestine. Liberals are still leaving in dream reality where she really does super care a lot, really, she just thinks you need to beg in exactly the correct way to not slaughter children.