Nonsense. The airline doesn't ask your marital/family status. They simply offer a bulk discount.
By your logic, Costco is also "discriminating based on marital/family status" by selling bulk at discount. Costco doesn't sell "buy 1/5 a toilet paper package, come back and get the other 4 1/5 later". They sell the whole package up front, use it or lose it.
That's how bulk discounts work.
Heck, you could say that a gallon of milk discriminates against you because you have to pay way more to buy a pint of it, and you can't "come back later for the other pints at the same price".
This is absurdism to the highest degree.
You are welcome to book flights with friends, or even organize a flight-share program and go in on flights with strangers. Bulk doesn't discriminate. I know folks who go in together on Costco bulk because they can't use it all. Make the system work for you.