Yes it's a money making scheme...
But perhaps not for the reasons some like to portray - sorry if some have heard what follows before...
The public have been shown to like cheap fares.
Many of the on-line flight selection/booking sites order the flights they find in price order, and/or you can select a range of fare prices you are prepared to pay....
So in order to get your custom the airlines have had to strip as much as possible out of the fares, and then try and recover the lost revenue through the ancillaries - speedy boarding, baggage charges, meals, seat choice charges.
Making money that way allows them to offer low fares but make some profit on the deal (not a lot, on average typically sub £10 a passenger)
if you ban charging for certain bags, seat choice etc then basic fares will have to go up...
BTW someone hinted at there being international regulations about child seating - some regional regulators such as EASA may issue guidance but mostly it's down to the natiional regulator (e.g. UK CAA, US FAA).