Well, automakers don't literally do that, but they might suggest you use the specific oil, coolant, or brake fluid that the dealer has. Sometimes much cheaper products are perfectly good and sometimes not. I have an old car that requires a particular type of automatic transmission fluid for the power steering system. People who don't research it and use generic "power steering fluid" say it can lead to leaking seals. The wrong type of radiator coolant is said to lead to all sorts of problems too.

The fact that there is a conflict of interest and the manufacturer will charge more doesn't mean that there aren't real issues.