Because companies don't really trust each other and have huge legal teams review 100+ pg contracts? Even internally trust is lacking at times?
It does have some efficiencies. They are likely tiny compared to separating money and state, like we managed to separate religion and state.
But I guess its all just buzzwords and speculation! All these people wasting their time on something so obviously useless. You should let them know!!
But that's not the real problem: the real problem is, how can blockchain contribute anything to this problem for them? The process of validating the origin of goods depends on remotely uploading certificates of authenticity - an artifact produced off-chain.
From that point on, nothing else matters - since it all depends on whether that certificate is legitimate, trust is external to the chain.
The rest does not require "blockchain" at all and is actively made more difficult by it - since every other step is just regular logistics tracking, something Walmart is very good at.
Again: what possible benefit is blockchain bringing here? The original artifact is off chain, the goods in question are offchain and the cited benefit is not "improved security" -- it's "quicker look ups". But...that would've been achieved by just scanning barcode numbers into a database at every location (which again: is trust, it's not a fact which is established on-chain).
So yes, I do believe people are wasting their time on something obviously useless - IBM was involved and their biggest contribution to my country was to call 25 million people logging on to do a census on one night a denial of service attack. Walmart executives aren't technical - they need to know "what the blockchain could do" and IBM sells them some snakeoil.
Private blockchain has never made any sense: you just give all your employees private keys and move on with your life.
EDIT: Which is to say, I'm sure a lot of people are saying they're doing it, and it is yet to be for anything more then to say "we're doing blockchain" to investors and the public.
EDIT 2: Reading through the Hyperledger case studies seems to bare this out as well - the implementations are comparatively small, and keep desperately asking the question "was blockchain vital to any of this, or was the actual innovation you just finally automated something into a database?"