> Why not subsidize the groceries instead, then?

Then you'd have the State giving money directly to the likes of Unilever (think tooth-paste) and big agro-business (think bread). Subsidising transport instead is the lesser of many evils.

> And let the market find efficiencies with reduced transportation distances.

Market doesn't work when it comes to most of us.

> Or better yet, just subsidize the poorest among us,

This is just praying to bringing in servitude amongst us, it will go like this: "we will stop subsidising your daily bread if you stop voting for us". The same goes for the idea of UBI more generally speaking.