Miners are the arbiters of consensus because they extend the blockchain.  They are the group who's interests are most closely aligned with the success of bitcoin.  They are the only people with a commitment.  Hodlers can dump whenever they lose faith.  Miners have to fight to preserve their investment.  If they do not do what is best for bitcoin, they lose BIG.  Who do you want in charge, fickle hodlers who can jump ship to a different coin if they screw this one up, or miners who have huge amounts of capital invested in hardware that is useless without bitcoin?  Every governance system in the world is minority rule.  Pure democracy is 2 wolves and a sheep deciding what to have for dinner and nobody is dumb enough to use it as a governance model for anything of value.  It would be even dumber to cast votes based on who has the most money.