Flights to Fargo

When a person checking in to get on the plane and they trying to get to bags on the plane that takes up room for everybody else who has one small bag if they have a suitcase they need to check it in underneath but people have small backpacks and there's no room for him because people are using two spots up plus I mean through seat so they can save money on the charge for checking in a baggage. The other thing is is when they have too big of suitcases and then they have to check them in before they get on the plane and don't get charged for that so everybody who got charged for one baggage and these people had to check them in before they got on the plane itself got by without having to get charged that's unfair