It's not about libertarianism, it's about a race to the bottom and apparently, there's more than enough people willing to sit in smaller seats if it saves them a few bucks.
I have been able to successfully avoid United for the better part of a decade and I fly Alaska and Southwest the most because I’ve had a satisfactory level of service as the norm with them, not because their prices are the cheapest- else I’d be flying Spirit airlines.
1. they're the only ones available for the dates/times we need
2. paying 40-150% more is prohibitive for many folks (and generally, is not a 'few bucks').
If we had 30 inch and 28 inch pitch seats, and you could choose, and people would pay, say $10 more for 30 inch, that might get us a bit closer to the original comment, but we're nowhere near that set of options.
We have no other options because most people don't care as much about seat size as they care about money. The market is working, here, it's just not working in a way that you appreciate.
It's that airlines don't tell you how badly cramped your seat is going to be, you don't think about it when buying, and people have a short memory unless the experience was so brutally bad that it fixes itself in your memory.
They should, at the very least, be forced to disclose the seat pitch on every flight, so people can make an informed decision - and then, yes, you can let the market decide.
At the moment there's no reward for offering decent seats, the airlines doing so are effectively at a competitive disadvantage compared to the ones which don't. This needs to change.
Only recently have aggregators started disclosing bag charges, which could be significant, especially with low-cost airlines (WOW, Norwegian, AirBerlin) outcompeting everyone else on basic ticket fare and appearing high in the results.
Now realistically airlines aren't thieves, they generally have a hard time with their profit margins, but that doesn't mean that they shouldn't be severely regulated.
No need to be redundant.