It seems to me that at one time fast food restaurants were a cheap alternative when eating out. Nowadays the prices in reality aren't a lot less(if any at all) than what you'd pay in a sit down full serve restaurant unless you go to a high end place. Now there are some healthier choices available but most of the foods offered have poor nutritional values and a lot of negatives for your health(both short and long term). They also push combos and try to get you to buy a pop(which is absolutely horrible stuff for your body).
The appeal of it is that it is tasty and quick. You don't have to think about it too hard when making up your mind on what to have and you can move on with your day. There is no planning involved and little effort. I used to be much like others in that I ate in places like that several days a week.
Over time and with effort I have weaned myself off of those places. The last time I went to BK(I hadn't been there in months) a couple of weeks back I had some deliciously decadent food that tasted good but left me feeling not so well an hour afterward. If you are going to do fast food there are better choices than BK. Subway is pretty good although their bread is packed with white sugar. Wendy's has a decent array of salads and such. For your own sake stay away from the burgers and the pop. Those are deadly and although the fries are not fried in trans fat anymore they are still very fatty and in most places the fries are coated with a sugar combination to give them that golden brown appearance.
So take some time to think about it. It will take time and discipline to change your eating habits. I have lost weight and my energy levels have improved since adopting a healthier attitude towards food. For me the benefits have been wonderful and I've saved some money too but there is more to life than money. You don't have to stop all at once. Little by little chip away at it and see how it makes a difference. Don't get discouraged and never ever give up. Start slowly and finish strong and healthy.