I'm primarily a "diesel guy" all three of the Big Three are building a solid, reliable truck these days. I've got a number of friends who are full time diesel mechanics and shop owners. The Ford 6.7s are by far the most popular with them. Even if their race truck is a Cummins.
Sounds like the...
I think that's the reason you don't see them much.
They interfere with the "normal" "truck things".
It's easy to forget that what seems normal or useful, can be odd or even a hindrance to the average consumer.
I've seen a few in person. You're right, they don't flow like a "regular" fiberglass cap, and they only come in black.
But somehow the two together combine to make a cohesive whole. They actually look better in person.
They don't look out of place, they look like a detail that's intentionally...
My personal uses are such that I need a 3/4 ton sometimes...
I looked a bit at a midsize daily and a 3/4 ton... Turns out that a midsize was almost as much as a half ton, but made some compromises.
But if you could wait a bit and get one of the new Rangers... I've been impressed with them.