I didn't say anything about base assumptions here.
No, you didn't, but I think it largely follows, anyway.
All talk of inclusiveness and modularity notwithstanding, a well-designed system, by in large does what is in its base assumptions. The farther something is from the base assumptions, the less you're apt to see it, and the less well the system will handle it, generally speaking.
Moreoever, if the base assumptions are along the lines of what the players want, then the more distant a thing is from the base assumptions, the less impetus there's usually going to be to develop it.