Election vs consensus

Dear list,
This is not directly related to erlang but for obvious reasons it’s pretty tightly related. 

I would like to understand why election algorithms such as bully are afaik deemed not enough to build consistent systems, hence the existence of consensus algorithms such as paxos/raft. More specifically in the creation of simple key/value stores.

I would have imagined that with leader election you can pipe all the read/write operations through the leader, hence implement consistency. However i.e. raft came in to fill this kind of scenario, and I would like to understand why it is needed. 

Does someone have pointers on things to read?

Thanks in advance,
r.