There are too many 'extreme points of view here.
Making people pay for checked baggage may tempt a minority to pack as much as possible into a carry on, but it's not the majority of people who will behave that way. Plenty of people travel on short haul flights for a day trip or a one night stop and don't need checked baggage, so again, I say, why should they pay for it?
The arguments about charging extra for a seat are, again, spurious and extreme. On the other hand, if you want a preferred seat, then pay for it or take what you are given.
As for the analogy "Should I have to pay for the testing of beefburgers for horsemeat" the fact is that we do. If I go to my butcher at the market who still uses a wooden block and charges £40/kilo for locally sourced fillet steak, I am paying more than if I buy Findus burgers, and rightly so.
If 10 strangers share a meal and I'm the one who has three courses and an expensive bottle of wine and liqueur coffee while the others have a sandwich and a salad, I don't expect others to subsidise my expensive tastes. The argument over ancillary services for flying is the same.