Mostly because it's (almost) all proprietary. None of the companies are investing in a truly usable solution. It speaks volumes that a handful of developers working for free where able to create a vastly better experience with yosys and friends.
The ability to fully enumerate and simulate every part of the design gives them a huge hardon even though stuff frequently passes simulation and fails on the silicon. It's very common to see FPGAs in nuclear, military RF, and aerospace applications.