this is a real conversation multiple people are having right now.
and another thing, how come i can’t get no Tang round here?!
I don’t have the two available here to do a side-by-side comparison, but here’s a suggestion: Mustard is not as viscous so it’s not too hard to get the product to the opening. Thus there’s not so big an advantage to storing it opening-down.
I don’t use ketchup at home, so I don’t know if the following applies to ketchup.
One problem I have with mustard is that it separates. If you store it upside down, you will get mustard-water if you don’t shake it first. But if you shake it enough to make a difference, you’ve undone the benefit of storing it upside down (the mustard is now all over the bottle, not down at the bottom).
I’m confused. I store my mustard upside down so I don’t get mustard water. The water rises to the top, you see, which if the lid is above, means when you invert it, you splooge out mustard water. Top down, the water is on top of the mustard as it’s stored, farthest from the opening.
Same with ketchup, actually.
My wife seemed to interpret it this way as well. That’s right. I found this thread interesting enough to explain it to Mrs. Mahaloth.
Basically, it is in the company’s interest to make it hard to get all the mustard out of the container, so they make it odd shaped and opaque. We have to go back to the store sooner to buy more. So, why they do not do this with ketchup is a mystery, hence the question about the ethics of it from our OP.
Are we right greenelf?
I think the core of the issue is this:
Ketchup is used in much greater amounts both overall and individually. It is often poured out liberally into its own ‘section’ on a plate, usually for dipping french fries into (if you pour the ketchup over the fries you’re a communist). **Mustard **is never used like this, it’s only squirted sparingly onto sandwiches. Many sandwich connoisseurs still prefer to apply it with a knife, hence the short, wide-mouth screw-top jars continued existence, and the non-proliferation of the ketchup squirt-style mustard bottles the OP is opining.
This all only applies to the US. Europhiles put vinegar or mayo or blue cheese on their fries (talk about communists!) 
I had poutine at a Fatburger today, not (as is usual here) as a meal in itself, but as a side dish with a Red Hot Buffalo burger. Usually I just apply vinegar, but I was feeling a bit faint today.
It is therefore my position that Canadian Fatburgers are innately superior to American Fatburgers. (Though to be honest they didn’t get the curds right.)
Maybe the OP means ethnically designed mustard bottles. The kind that are woven by hand from the bark of the N’Tengwe tree by a worker’s collective, using indigenous lore passed down the matriarchal line and funded by lines of microcredit.
ETA: “Before, we had just one chicken and I had to walk three hours every day to get water. Now, because we can sell our mustard containers, we have three chickens, a light bulb, and a bicycle. One day we hope to be able to make Miracle Whip jars and then we will get a buffalo.”
BUMP
Uh, green elf, can we find out what you meant?
The place where I shop stocks top-down ketchup, mustard, relish and tartar sauce. I use them all the time . . . except I don’t store the ketchup one upside down, because water accumulates on the bottom.
As far as I know, this is perfectly ethical.