Hand baggage only is not a solution.
Unfortunately most people require at least some things to be packed into hold luggage, not least because of the ridiculous security rules around liquids that prohibit holidaymakers from taking suncream etc in hand luggage. It is not cheap to buy this locally, if at all in most European charter destinations.
No doubt those travelling on flights with airlines such as BA may also be going for extended trips etc so need a lot more than 1 rucksack of clothes.