Does no one understand economics?
*The least I've seen is about £6, and it's often more than that. And that's £6 per person, per flight, so a family of 4 is looking at an extra £48 and some airlines/routes charge a lot more than that - someone has mentioned £200 to pay for their holiday, which is a lot extra and not fair to call someone cheapskate because they don't want to pay it.
If you've booked your holiday and sorted your budget, it's a bit of a shock to find these added fees at check in, *
In the first place it is very easy to ascertain fees in advance. If you are shocked then that's on you, not the service provider. Do you buy other things without finding out the price, and then complain about it?
In the second place, if you can't budget for the entire cost of the trip, then I guess you can't afford the trip, eh? Why should anyone else subsidize you and your offspring so that you can get the holiday you feel entitled to?
Would you expect a beef roast at the supermarket for the price of a sausage? And tell the cashier to charge the difference to the person in line behind you?
There is a cost to sitting together. Accept it and pay the cost. If you choose not to, hoping to bully your way into adjoining seats, then you are the scamster, not the airline.
(all "you" general, not directed to any one poster.)