Uh... Not sure you understand the situation, example: PAL charges you $50 for a ticket. If you fly, you paid $50. If you don't show, you pay the no-show fee IN ADDITION!
The cost to the airline is marginably lower when you don't fly (weight, fuel, food, drink) then when you fly, yet they charge you extra for not flying. There is absolutely no reason to charge that fee.
And the argument "they could have sold that seat" doesn't make sense either as you paid for it and they have no right to sell it again...
The no-show fee is a total scam...
I think you are the one who misses how this works.
If you do not use the ticket, it is available for use on a future flight (or possibly refunded) subject to a change fee. If you do not show at the gate, then in order to reuse or refund it you owe an extra $50 on the change fee.
If you do not care to reuse or refund the ticket, then you of course owe no money.