They call them ornamental citrus trees around here. They grow smaller and are easier to maintain than non-GMO varieties. But you are right, they serve no real purpose other than smell. Looking back, the terms "easier" "convenient" seem to be what get us into trouble time and time again.
Some people do use the fruit to make marmalade's but they have told me it takes .5 to 1.5x more Sugar than regular recipes because the fruit is so bitter.