Its not only the LCCs that charge for check in baggage, nearly all airlines do!
The latter do so because the former started it and did not see a top off in pax figures: = more profit.
Many flights are being dispatched with more cabin bags having to be loaded in the hold than were check-in in the first place; due to not enough cabin locker space to accommodate them all!
The original concept was to reduce costs or increase profits. Same effect. It was sold on the basis of 'pay for what you get, and don't pay for what you don't need.' The idea was that so many LoCo pax were travelling for such a short time that cabin luggage would suffice. Great until 189 pax turn up with the standard bag and they don't all fit. (149 max) The last ones are loaded in the hold for free. Cue whinging pax who paid. Cue whinging pax who have to wait for luggage. Great idea that evolved problems.
What we never learnt was the cost to the airline for 20 bags or 50 bags. Do the handlers charge per bag, per trolley? What? It takes 1 crew to load 10 bags or 100 bags. The difference is time not personnel. The reason some LoCo's use only one hold is cost; it's only 1 crew. Others load both holds = 2 crews. I assume more expensive??
What is the most irritating & frustrating issue is the different cabin bag sizes. OMG. And they keep changing. 5cm here & 5cm there from different dimensions. And none of them are standard ICAO recommended sizes; AND they fly the same aircraft. PLEASE! It's supposed to be a customer service industry. It's time the customer took it back. The pettiness of differing cabin bag sizes by 5cm is childish, and the ridicule at the gate from the baggage police is absurd. If it was a restaurant you would never go again, no matter how cheap it was. Why do people want to be stressed out and embarrassed? To see OAP's treated like school children by youngsters young enough to be their grand-children is sickening.
Let the revolt begin.