I assume the airlines have done the math and the time cost is less than the increase in revenue.
All that said, I almost always fly carry-on only, for my own convenience (no waiting at baggage claim, no lost/damaged luggage, etc). I often wonder what on earth some people are taking with them on vacation - I can do a two week vacation with carry-ons (1 luggage, 1 small backpack), and that includes a bicycle kit (helmet, shorts/jersey, shoes, and pedals) on top of normal clothing.
The "right" answer would, of course, be to charge for carry-on luggage too. I think some airlines are starting to do this now. I bet their customers won't be happy though.
Right, but that's an artifact of only charging for one of two "cost-adders", when they're close substitutes.
It doesn't refute the general point that it makes sense in general to charge more for things that add legit costs; the problem here is that they're not being consistent about it. Per previous discussion, charging for carry-ons seems to make more sense than charging for (a moderate allowance of) checked luggage:
But what happens to, say, the electricity used to melt the aluminum before being poured into molds?
If there's some tax benefit to splitting a fuel surcharge out, obviously taxes on fuel aren't an ordinary VAT...