I know you can boil pasta in wine, but tomato sauce has a lot less water in it. Anyone ever try this?
Perhaps a real cook would have a different term than “boil,” but sure. Think of all the hamburger helper noodle dishes – they cook the pasta along with other stuff, including sauces.
That is more or less how I do lasagna. I put unboiled lasagna noodles in the dish with the sauce and meat and cheese. It will probably work but you will need to experiment to get the time and amount of liquid correct.
So why am I bothering to boil the pasta, strain it, and then covering it with tomato sauce when I could just do it all in one shot? There must be some difference.
Maybe eliminating the starch that is in the water?
If you boil tomato sauce for 10-15 minutes you’re going to reduce it considerably, changing the texture and taste.
Also, if you are completely immersing your noodles in sauce, you’re using way too much sauce. It should really be a dressing for the noodles.
Exactly. I can’t imagine soaking pasta in that much sauce.
I usually make spaghetti and sauce in one pot however I do the following:
-Fill large pot half way with water, add a bit of salt and a bit of olive oil.
-Bring to boil, add spaghetti, cook till done.
-Dump contents into strainer in sink.
-Put jar of sauce into still hot empty pot.
-Put pot back on hot burner but reduce heat to a simmer, sauce will heat and bubble almost immediately.
-Dump cooked spaghetti from strainer back into pot.
-Mix and your done.
From experience, it takes longer and the texture isn’t really the same. (Though the pasta does taste a bit tomato-ey.) It’s an osmotic pressure thing I think - water flows into the pasta more slowly if it’s in a thick emulsion of tomato stuff versus pure water.
One thing that I’ve tried myself is ‘parboiling’ the pasta in regular water for about half the time it would take to fully cook it, and then tossing it in with the tomato-meat sauce for the rest of the time. You still get a second dirty pasta pot that way though. 
The proportions are different for different recipies. For Italian pasta, a dollop of whatever kind of sauce is traditional on a plate, not pasta swimming in a lake of soup.
OTOH, some dishes, like casseroles, have different proportions.
IANACook, but maybe it’s similar to why we don’t mix ketchup with fries and fry them together (Mickey D’s tried once and it didn’t sell, IIRC). It’s a cultural preference for the way things look and taste when combined differently?
Also, you could burn the sauce if you cook it long enough to soften the pasta. Doing them separately, you can prepare each just right, under different conditions.
You really should try it. I am sure there will be differences in taste and texture you will have to decide which way you prefer things.
That’s “making”, not cooking. 
[Italian accent] You want to taste-a the pasta!
For the record, that’s more or less how I make my version of minestrone: make a tomato/bean soup and then toss in macaroni for the last 10 minutes or so.
But this only works well because the final product is more like soup than thick tomato sauce, and even then you have to be careful to make the base thin enough, because the noodles absorb a lot of water. If you just made regular thick tomato sauce and added the noodles, there wouldn’t be enough water (probably the noodles would never cook properly, and in the meantime the extra thick sauce would burn).