Because most of the free market theory that most normal people believe is based on the assumption of perfect competition[1]. However, that almost never actually occurs in the real world and even ends up being impossible in most cases.
For example, there is always going to be a huge barrier to entry for automakers. They need to invest an enormous amount of time and money in design, factories, raw materials, labor, etc before they can deliver an actual car. This barrier protects automakers from feeling the full repercussions of their anti-consumer practices because it is extremely difficult for a new pro-consumer competitor to enter the market.
When we remove that assumption of perfect competition, the whole free market theory starts to fall apart. A well functioning free market requires power to be balanced between all parties, otherwise whoever has the most power can end up corrupting it and using their power advantage to grab even more money and/or power.