[zebra 23215] Query on why Zebra is required !!!

Hi Experts,

I am beginner, trying to understand the Zebra about its purpose and other details.
Can someone please clarify my below doubt.

1.      Why do we need to have Zebra (routing manager) required ?
Can't we have individual routing protocols say BGP, OSFP,RIP ect to run and participate in the routing and update the Kernel routing table directly?

Thanks and Regards
Anish