Since there have been multiple 0-day in kernels, we should drop all security boundaries in them because you'd only need execution on the machine and a known vulnerability.

Since there have been with bypass on service X, we should remove auth because all you need is the vulnerability.

Address space layout randomization wouldn't exist with this mindset, and yet it does and helps for many exploits.

SGX is not fully secure. But neither are the other part of the stack. Security (or trust in this case) is done through layers because it's a question of when you'll be vulnerable, not ifs.