Emirates charge rather more than £2.
And multiply that by more than one passenger.
And I can recall SirTim Clark talking on the in-flight audio about this and anybody who hadn't flown before might have thought he was talkign about a new ffacility where previously airlines didn't sit people together but now they could.
It didn't seem to be an issue over thelast 30 years + that I've been flying until the online technology allowed them to sell this feature and the copy cat nature of the marketeers in the business means they all pile in.
The airline industry as a whole has been fairly despicable about this.
It suits them to turn this into a 'fear sell' for families. So even if they are not doing anything deliberate they are encouraging some customers to pay out of concern.
My feeling is that government could do something simple. Air tickets are VAT free. Any extras such as 'speedy boarding' or seat selection should be liable for VAT. That would give the airlines a bit of a dilemma.