The simple reason is because they can. If you need that flight or that extra luggage then you will pay for it. If not you choose an alternative airline that doesnt charge for the extra bag. You can choose a cheap lower class airline that doesnt have all the perks or you can pay more for a comfortable flight with all the bells & whistles.
Upcharging blah... quit beating this dead horse. Your cheap all the hookers know it. You have 107 reviews about banging "cheaper" pussy so wtf is the problem? Hookers are gonna charge what ever they want, you dont have to see them. You dont wanna pay the rate move on you dont have to book. The only upcharges I typically see are for greek. That is not a typical GFE service.. so if she wants to upcharge for greek she can. Those that want it will pay..those that dont wont add it. If your flying coach but want a bigger seat, better food, drinks etc you pay the upcharge for 1st class if not you sit your ass down and get what your able to pay for.