Gravy is an entirely different animal. Yes, it's mostly flour and corn starch, but it's also not the star of the dish the way that tomato sauce is.
I don't know anybody in my family aside from my Gen X sister and millennial cousins who can't make gravy from scratch. My "Greatest Generation" grandmother in particular only cooked about 30-40 dishes, but she cooked them so regularly that she didn't need a cookbook, and they were never anything but great (except when she tried to feed me frozen pizza when I would stay over for the week. She'd throw American cheese and ham on top because she didn't believe it would be filling enough).
I don't get why people would use flavour packets when making gravy, or why people would use corn starch.
Not saying it's wrong, but that it seems unneeded.
For example, let's say I fry up a pork chop. I may put 1/2 a spanish onion in the pan, and I'd definitely add some cayane pepper and mustard powder. Maybe some fresh garlic.
As the cooking nears completion, I'll add flour over everything, until all the juices and grease is absorbed.
At this point I want to brown the flour a little bit. My heat is little below medium, I want browned, not burned.
So, I try to flatten the flour against the cooking surface, spread it out, make sure it gets heat.
This takes maybe 4 minutes, with me making sure the flour gets moved around, re-flattened, mixed up a bit, so it all browns.
When ready, add in cold water. The amount is try-till-you-learn amount. If it starts out too thick, add more! Now set pan to full heat, and stir repeatedly.
When the water is hard boiling, keep stirring, making sure that during this entire process you are cleaning the bottom of the pan.
If you're using nonstick, instead of stainless or iron, you probably can't do this right. You need to scrape the pan here. You need to forcefully agitate. Right tool, right job.
You may need to turn the heat down a bit, as things thicken. Again, you need to start thin, make thick.
(When you first add the cold water, it will be very water like. Thin. But what happens is the flour breaks up, and makes it thick, so first timers will need a lot more water than they think.)
Two things will happen here. You will collect all the flavour from everything you have just cooked, and the gravy will start to thicken on its own.
No corn starch is required, or flavour packet. Full, lush, flavourful, thick gravy, no lumps, cold water is part of this, and the hard boil after.
It will take a few tries to get it right, but once learned, all things become gravy.
Note: thanks for lettimg me hang my comment here. Also hi.
I think this phenomenon started in USA with the "Betty Crocker" and "Bisquick" product line. This was marketed as easier than scratch cooking. There's nothing wrong with the concept (I'm sure there is a box of Bisquick in my kitchen), but it doesn't always make sense from a value standpoint. Also it is less flexible. You could apply the technique you describe no matter what you were cooking, and you could vary the timing and amounts a great deal. The "kit" stuff is more like a chemistry demonstration, which must be carried out fairly closely to the directions on the box in order to remain somewhat flavorful.
I think it really extends to everything, others have mentioned pre-made tomato sauces here, also baffling both for price and taste.
When I left home, pre-internet, and started grocery shopping for the first time, I recall wanting spagetti. Well ground meat, that made sense. Pepper. Salt. Noodles.
But until years later, I didn't think about the spagetti sauce I bought. I just kept buying it. It was just there, labelled as a natural ingredient.
You want to make spagetti? Why, there's the sauce!
In retrospect, I think labelling is quite effective in this way. Get 'em when first out of the house, latch on to their inexperience then.
Starch also has the nice property of tenderizing meat and locking in juices when used in a marinade, in a process called “velveting.” https://www.bonappetit.com/story/velveting-meat/amp
The traditional starch is water chestnut, and you can still buy it, but corn is a lot easier to turn into a starch.
In general, a lot of things went via the Pacific as well during the Columbian Exchange. East, Southeast, and South Asian looks very different without chilis, tomatoes, or sweet potatoes to name a few.
Just another example of fashion in food—lard is coming back in fashion as an ingredient in home cooking, and in the UK, brown sauce is going out of fashion.
I literally do have multiple boomer-generation family members who cannot make a gravy from scratch. The "greatest" generation folks in my family, while we still had them around, were also not outstanding cooks. They had an excuse, because they grew up in shotgun cabins eating government commodities. I'm not so sure about the boomers...