I don't know about the rest of the world, but in the Middle East flat kitchen sinks are standard and ubiquitous. I wouldn't be so quick to assume that it's an aesthetic design decision — I bet it's more of a cultural preference.
I don't like flat sinks, but I can see how some people do. In Lebanon they generally build large flat sinks right into the countertop with the same marble. They are much larger than most American sectioned sinks and are good for certain things. They use a small squeegee to clean up after everything is done.
Kitchen sinks are a bit different. They are deeper, you don't shave in them, and they are typically sloped a bit so that they don't get small pools of standing water. These new bathroom sinks are pretty bad. They are really trendy in hotels along with the water found style sinks and the ones that look like a bowl sitting on top of the counter top. Every one is a regression in usability solely for the sake of aesthetics.
One day we'll look back on this design trend and laugh. Too bad it will take decades before these poorly designed items are replaced in homes and hotels.
God I hate those. The counter is either at your knees or the bowl is in your face. There's no where to put anything and simple tasks just end up being a mess. What a stupid idea!
Flat (edit: okay, flatish) kitchen sinks, as opposed to bathroom sinks, are ubiquitous in North America too. In the kitchen, the flat sink is useful for dish-stacking.
In Sweden... You have a sink split in two sections, one that you filled with dishes+water, one for rinsing. My parents yhsed a dishwasher, and I later had a dishwasher as well.
In the UK, my sister uses a wash bucket. This is the only place I've seen this.
In Greece, dishwasher again. The sink is also split like in Sweden.
In Japan, washing dishes in a single large sink under running water.
Edits:
* The UK also has those braindead hot and cold in separate faucets on each side of the sink. So when you wash your hands, either you're wasting a ton of water, you're using cold water, or you're scalding your hands. Will never understand that. And this is in a NEW apartment!
* Also, many brits I've known don't rinse their dishes... they let them dry with the soap on them. Also inexplicable.
Depends on the sink. If you've got a sufficiently large countertop, it's not uncommon to have a steel sink comprised of two basins, one for washing/soaking the other for rinsing.
Older construction with porcelain or enameled sinks often have a single basin. Both this and the finish make a removable plastic washtub useful both to protect dishes and allow for rinsing whilst washing. Some "efficiency" apartments may also have smaller sinks for various reasons and only offer a single basin, again, a washtub can be helpful.
The few I've seen have been people with only one sink (so, a single large depression), which makes it easier to wash and rinse. But if it's not large enough, none of them fit, so it's mostly an exercise in futility.
And yes, dishwashers are absolutely everywhere. Some don't have them of course, but they're standard fare in a huge number of places, even relatively cheap apartments.
Yes, that's exactly it. I find them pretty annoying because water and food debris builds up in the corners and it's hard to get it all down. Could actually be a feature and not a bug, — I've never seen a garbage disposal there, so you don't want all the food going right down the drain.
Garbage disposals are essentially unknown in Canada (except on US-originated TV shows), and we use essentially the same sinks. (It is possible to purchase and install one, but I have never seen one installed in a home.) Food (at least appreciably large chunks of it) is prevented from going down the drain by the basket strainer that is part of the plug (which isn't completely removed when draining the sink). The strainer/plug is them emptied into the food waste/compost container that is in the kitchen anyway.
A traditional kitchen sink style is "The Belfast Sink" - an image search shows these to be big and flat style sinks. Not it's not just in the Middle East.
In the UK these kinds of sink were/are often used in conjunction with a smaller bowl that went into the sink [1] (less often these days). The sink has multiple functions in addition to washing cutlery, plates, etc. Sometime quite large things are washed in the sink, however when typical dish-washing is being done, a smaller bowl in placed in the sink to economize on hot water as well as to bring about the other advantages that OP claims for a curved sink.
Flat kitchen sinks work mostly because the facuet in kitchens usually swivel, so that you can move the flow of water to flush things out of the corners.
In my own apartment I have a directional, tilting head [1] attachment. It lets you point the water stream anywhere within the sink, and it has a secondary mode that turns the stream into a wider shower-style spray.
I have a flat sink in my bathroom. It's slighty sloped, but that doesn't help much against gunk collecting in the corners; it's awful precisely because the faucet doesn't swivel, and the faucet is one of those low, short bathroom types, so adding that same attachment would not help much.
I don't like flat sinks, but I can see how some people do. In Lebanon they generally build large flat sinks right into the countertop with the same marble. They are much larger than most American sectioned sinks and are good for certain things. They use a small squeegee to clean up after everything is done.