Cheap painters

Why would anyone use cheap paint? Or better yet why would anyone not use a primer? Primer is cheaper than paint and has better adhesion than paint does. Take the paint at Lowes they have two brands: one is Olympic which is the cheap stuff, second is the better stuff which is Valspar signature series paint. The coverage is good and the cost is reasonable. What I don't understand is why any painter would use cheap paint instead of the decent stuff. The price difference is only about $10 per gallon of paint so they aren't saving much money on material. I guess it's just because they want to cut as many corners as they can. So next time you get a cheap paint bid ask them what type of paint they intend to use and tell them you'll pay the extra $10 a gallon for the good stuff.