Some people buy "better" food than they would typically serve their own family when hosting. This can be for many reasons: trying to impress others with good taste/health, a splurge because it is a special occasion, or fear that your guests will not like the "lower" quality you eat. Some people like to take special time to prepare more time consuming food/prep when guests will enjoy the fruits of their labor as well.
I would say serving the same food is probably an exception for most people. Even for me this option is used the fewest number of times in comparison to better and worse food. Some people might just keep on buying and serving what is habit and comfortable for them. In reality, this makes sense, especially if you aren't trying to keep up with the Jones'. The perk of this option-you are totally comfortable with yourself and what you like. The downside-you aren't getting anything different or new to try (and you aren't saving any money by purchasing "worse".)
Ok. This one is pretty obvious. I am going to put it out there as truth because I have never heard of any other reason for doing it other than to-SAVE MONEY! If you are hosting for many other people and trying to offer a variety of food why WOULDN'T you try to save a few bucks by purchasing in bulk and/or lower quality food. In contrast with "better" food, I would venture a guess to say that your amount of prep time and cooking is going to be less with "worse" quality food. I don't think there is anything wrong with this. You get to enjoy your company without worrying that you will over steam your fresh vegetables by 2 minutes too long, while forgetting to turn down the grill temperature on your delicate meats, and while also forgetting to add the garnish to your dip that had to be prepared exactly 14 hours ahead...
Ok....I'm being a little prejudiced. I do suppose my preference is "worse" quality food ONLY for the reason that I want to have a good time and not need to worry so much about the timing and every little detail that generally is required of "better" food. I like a variety of all the foods though. For my get together, I am going to buy "better" foods that don't need much prep or maintenance as well as some "worse" foods that will allow me to need to spend less time cooking and serving it.
So, does that mean some "better" + some "worse"= "the same" ??? I think that "the same" might be the net result.