Kaidou has been eating accumulated damages for 30 chapters, yet it will need Luffy no less than 10 more chapters to fully defeat him.
Big Mom has yet to take a single damage, she has literally taken no damage.
So unless Oda wanted to prolong this arc into another 40 chapters where Kid slowly started to damage Big Mom into her defeat.
Especially since Oda has Luffy stated multiple times to multiple characters, even Big Mom herself, that he's coming to defeat Big Mom AFTER he's taking down Kaidou.
At best Kid is gonna stall Big Mom till another plot that forces her to be removed from Wano (a.k.a the red poneglyph).
Hell, Kid wasn't even there when Luffy figured it out the secret of Advanced COC.