Because when a restaurant buys vinegar, it comes in a gallon jug, if not a five gallon bucket. Hell, it might come in a 55 gallon drum. But then Blue Apron puts it in single 1 oz bottles and ships them all over the country, wasting a huge amount of packaging to supply commodity ingredients.
Take out dinner in itself is not a thrash concept. Something like Blue Apron is. A thrash concept producing thrash. You don't have to cook with takeout. You have to cook with Blue Apron, spend extra money on groceries and produce extra thrash when the entirety of it is avoidable. And if you are nearly a good cook and follow the instructions on a prepackaged thing, you surely can go and shop groceries and cook better meals. So this kinda solution is not for the lazy (take-out crowd) and neither for the home chefs.
1 quart of white vinegar = 80 cents for a supermarket brand. If you want organic Sprouts white vinegar it's $1.80. If you need something like rice wine vinegar, ~$2 for 12oz. Anyway, the point is that they must be making a huge mark up even if they charge 50 cents for 1 oz bottles of vinegar.
Don't people poach eggs? You need vinegar for that. Boil a pot of water, two capfuls of vinegar, crack 2 eggs into something like a 3/4 cup measure, turn heat off wait for water to stop aggressively boiling, lower the measuring cup of eggs so it partly submerges, tip it to empty the contents (you don't want to drop the eggs in from altitude), lid on the pot, set a timer for 5 or 6 minutes. Play around with the time. It'll take less time if you have a stove with residual heat: glass or coils. It'll take more time if you have gas or induction.
If you do it a bunch of times, you can figure out when they're done the way you like them just be jiggling the pot and seeing how the eggs move under water.
The fresher the egg the more it will hold together. If it flattens out on the bottom, oh well some eggs do that even with vinegar. You'll get over it.
Next start making homemade bread for your eggs. And now you'll be willing to pay $6 for really good eggs from chickens that eat insects. OK I'm carried away now...