Why Airlines Oversell Flights

If the airline industry is truly parasitic, they aren't doing a very good job of it. In 2019, North American airlines had an average profit margin of 9.1%. The average profit margin across all industries was around 10%; it's unfair to suggest that they have an obligation to increase costs in such a way that would make their profits well below the overall average instead of only slightly below it. You haven't provided any numbers suggesting they could afford to rectify the problems you identify anyway, so for all I know the only way they can operate in a non-parasitic fashion is by not operating at all.

As for your specific examples of "parasitic" practices, overbooking is done to keep prices low. For every sold-out flight, there is going to be a certain number of no-shows. So they'll overbook the flight to ensure that all the seats are filled even if a certain percentage of ticket holders don't show up. The airlines only make money on a flight by flying a full plane; they aren't going to take a loss on every flight that someone doesn't show up for. They can estimate to a reasonable degree of accuracy how many people aren't going to show up. If you don't like the idea of oversold flights, the alternative is that the tickets will be priced so that the passengers who are expected to show up will cover the cost of the no-shows. Given the incredibly low risk of being involuntarily bumped from a flight, it's worth it for most people to take their chances on an overbooked flight rather than pay extra every time they fly. Additionally, if you get bumped there's compensation involved anyway, so it may actually be to your advantage if you have a flexible travel schedule. If you're really in a hurry and don't want to be bumped then you have the option of flying business class or first class, where the already small odds become infestissimal.

As for delays, they are usually simply unavoidable. If you want to be compensated for these delays, you have the option of purchasing travel insurance that has delay coverage. If you don't want to deal with the extra cost, keep in mind that if the airlines were to provide every passenger compensation for every delay, they would effectively have to build the cost of travel insurance into every ticket sold, so you'd then be paying for travel insurance whether you wanted to or not. This would also be an option if you were really concerned about being bumped from an overbooked flight.

Finally keep in mind that these kinds of restrictions aren't unique to the airline industry, it's just that the time-sensitive and stressful nature of air travel makes us notice them more. For example, every grocery ad you read has all kinds of restrictions you'd never think of. If a circular advertises a product at a certain price, and the store doesn't have the product in stock, they aren't required to provide it for you, even if they don't include limiting language like "while supplies last", etc. You may be able to get a rain check but that's a courtesy of the store, not a contractual requirement. There are consumer laws preventing things like bait-and-switch schemes, but those cover particular circumstances, not just run-of-the mill shortages. Similarly, if an item proves popular and the store wishes to avoid the foregoing scenario they may put up a sign limiting purchases to two per customer or whatever. If you showed up expecting to stock up on the product you can't make the argument that you're entitled to their entire stock just because of the ad. There's a principle in contract law that states "the offeror is the master of the offer". As u/Evan_Th notes below, the problem is that you didn't bother to consider what is actually being offered. The airlines aren't flying passengers as a public service; they're doing it to make money, and they aren't going to make an offer that loses them money on average.