I'll never understand why they don't just put the cheese directly on top if the meat so it gets all melty and delicious. That's how I do my tacos at home: It goes meat, cheese, hot sauce, lettuce, cilantro, then pico, in that order. Don't forget to fry shells yourself using corn tortillas. Don't buy that pre-made Old El Paso bullshit.
The real answer is because they don't look as good. Marketing decided they look sad and pathetic if all you can see is lettuce, since the amount of cheese and meat is so small anyways. They want you to SEE it has cheese. They don't care if you can't taste it because it's on your lap.
The far superior Crunchwrap Supreme was practically engineered to solve every case of taco mishap imaginable. Crunchy, tasty, and sh*t doesn't fly everywhere when you bite into it. It even keeps your hands relatively clean. If you must eat in your car, this is the way to go.
The only flaw is it doesn't have a good way to inject hot/medium/mild sauce into the envelope, and I'm pretty sure you can't order it prepared that way.
You can. I worked at Taco Bell, and our managerial training had/has an entire module that boils down to: "if we can reasonably do it, and the customer asks, then do it."
That's the one with the soft taco shell bean-glued to the outside? Solid compromise to prevent taco-shell shrapnel from ejecting all over your lap. Doesn't fix OP's cheese problem though.
The taco is just an objectively inferior vessel for transporting food to your mouth. It has two whole open sides that are level with it's base and it's open to the air all across the top. It wouldn't matter what you put on top. It will still spill out. You have to turn your head 90 degrees horizontal to eat a damn taco. Burritos are superior.