If heart disease and stroke are major concerns, then how come fast food restaurants don't use "good" fat oil?

Profit plane and simple
There is no profit in using good oil to cook with. When the buyer don't care all that much

Cause if they did they would not eat there would they then

Profit would be down because of it Then it would be necessary to use what the customer wants or be out of business.

So it is the public who are the culprit here
Not the fast food restaurants.
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because they are cheap bastards that dont care about our hearts or arteries

Honestly.. it's not a law for them to do so, and the vegetable oils they are using now are cheaper compared to if they went to a healthier alternative.

It's all about the money.

because 'bad' oil is cheaper

Fast food only care about revenue, gaining profit so they have more money in their hands. The bad oil is the cheapest. Fast food is bad for you anyway, good oils will not make that much difference.

Some are switching, have already switched, or are researching how to make their product taste the same with better oil.

They're (half-heartedly) trying.

I guess we are lucky. The State of Virginia is changing the fryer oil in all fast food restaurants and collages in my area. The collage started first.

There bastards who don't give a **** 'bout our health only want those green pieces of paper!

like others have said, the oils that are bad for us are cheaper. also, lots of people are very ignorant and do not know what is good and bad fat.
good: saturated fats -these are the animal ones like meat, eggs butter etc. and YES you can eat them.
also some other monounsaturated fats are good like olive oil. foods with good fat are butter, coconut, bacon, chocolate, red meat, real ice cream, olive oil, BUTTER again, nuts, WHOLE WHOLE WHOLE milk. and others.

bad fats: trans fats, aka MARGARINE AND LOWFAT MILK. never eat those. there are also other bad fats like anything processed, but again, processed foods are cheaper.