Decisions, not options, is a mantra you'll hear around here.
When I develop a site I do so knowing where the site will be sitting on my client's server, and the site structure need not be changed.
You do. We don't. We can't. There are over a million WP users today. I would put dollar down that no two have exactly the same setup. And because of that, the best way to support all of them is the way that's been done.
Why not offer my suggestion for sites built and migrated where such complexities are not going to be an issue.
Because the users don't know they're the site that will have an issue.
Searching for domain.com/wp-content/uploads/ is not easier or more reliable when you start moving things around.
Sure it is, because of how WordPress stores your uploaded images. They are always in 'a' location. Single. It's normally
/wp-content/uploads/, but yes, you can move it. When you move it, say to
/sneakycontent/myuploads/, then you search/replace any extant posts, fix those images, and all your new ones go to
/sneakycontent/myuploads/ - Everything's fixed.
A multi-site installation would be a problem, but that could be addressed in the admin set up which would use absolute links, and we would use search and replace.
That code would be way more problematic than the shenanigans to make relative image paths optional, without breaking the myraid types of installations.
Basically you're the minority with your setup. Sorry :/