On the other hand it means you can have partial ownership of things for a slice of time. As in housing rental, it offers flexibility (the alternative for people who can’t afford to build an average house is to build a shanty...
Do I cost an airline more money to transport me out on a Monday and back on a Friday than the converse? (I suspect not, but not staying Saturday night makes the former ticket more expensive on many carriers.) Does SSO really cost as much to provide as the “enterprise pricing” tier suggests?
Those higher priced business flights or enterprise tier purchases help subsidize the lower cost options, making it possible to sell a base version and a deluxe and get enough revenue to make the economics attractive.
I remember years ago shopping for a Jeep Wrangler. There was a ~$175 option for a larger gas tank (22 vs 18 gallons or so). If you bought the option, you got the same physical tank and a shorter pipe from the filler into the top of the tank (so more fuel would go in before the pump clicked off). To the buyer of the Jeep, that option was worth something. I’m OK with Jeep offering it. (I wouldn’t buy it, since you could easily install the “larger tank” with a hacksaw, but I’m sure many did.)
Your analogy of the gas tank is exactly what is not happening. It would only make sense if you had to pay a monthly fee for the extra 4 gallons, and failure to do so would cause your tank to fill up earlier.
The purpose isn't to subsidise poorer customers though. Rather it's to maximise revenue.