They exist because they're a powerful lobby who can bribe laws onto the books that say cars need to go through dealerships or provide other roadblocks to direct purchase. They add value to their own pockets by being a useless middleman.

I hate them, but if you treat it like a game and operate within their rules it can be fun instead of a pain. I think if it a lot like poker. I sure would bluff my own grandma to win a pot. Same thing in car buying. They aren't your friends but your adversaries.

I have bought 7-8 cars of my own over the years and helped 4 friends buy cars because they know I love doing it.

First, if at all feasible bring several thousand dollars cash, no matter what your goal is. When you buy a car without cash the sales people get their cut at the end of the month in a lot of places but if your cash down payment is large they will usually get their cut immediately and this puts them a little more on your side at the close. Make sure you show them the cash when you're safely doing a test ride and tell them you want to give it to them! Don't do this if you can't do it while feeling safe i'm very large and do car shopping mostly in big safe city areas.

Second, don't ever fall in love with a car. You always have to be prepared to walk away from a bad deal. And in fact you will find that your willingness to walk away can often get you a better deal. I balked once over a $300 dealer fee, that only popped up while signing paperwork. They bitched at me, a lot, (we had been at the deal for about five hours) but they got the fee worked off.

Third, do not ever let them get you into the 'four square' that's a suckers game. Negotiate the price of the vehicle directly or go to another dealership that will. I have been forced to leave when the sales guy told me flat out the four square was a requirement at their dealership. Smart for them but lame for you it's like playing a complicated game for the first time against someone who plays it many times a day and is hugely financially incentivized to confuse you with it. Refuse it.

If you are buying a new car (which i don't really recommend) wait until they have given you the absolute rock bottom lowest price. Then tell them that you think there's still a little room. On speakerphone call other dealerships in your area and tell them the price you're getting offered on that exact make and model. If it's actually a good price they will tell you they can't beat it. I have been invited across town to save $1,000, whereupon the now angry sales manager agreed to match that price. You gotta do it on the speakerphone with them hearing the better offer though or you'll have to drive to the other dealership. They have heard that 'it's $1000 cheaper over on the eastside' before.

Don't be rude, don't be an intentional dick, but play their sleezy game with their rules and you can save a lot of money.

It's a shitty system that should be abolished.