Actually, it's not true. Selling votes is the equivalent of purchasing advertising space on a billboard, racing jersey, etc... Those with valuable content, but not enough steem power, it is the only way to get noticed quickly. In Steem, users with the most steem power, followers and votes, trend to the top. The rich just get richer and the poor stay poor.
Voting bots offer the ability for users with quality content to remain competitive with others that are hoarding all the voting influence. Voting bots actually make things fair for new steemians. It's economics.