The alternative is even worse: unelected corporations having a monopoly if  not on state violence then on technological, psychological manipulation and control of populations, as we have seen facebook, google and amazon do when EU doesn't step in. Voting with wallets has its limits when the only place left to buy essential things is corporate supermarkets and tech companies.  Where are you going to get your computer chips from when only 2 companies sell them ? 

 Monopolies arise mainly due to State support and friction given to potential competition due to regulatory compliance.
Big Tech would definitely not exist without that, at least not at today's scale.