2.- Best features/cost relation.
3.- Passed all our tests.
Until now, there was no known policy against other system, even if they didn't support it. You could use their boards as long as your system adheres to the same standards the board was supposed to support. With this statement, Gigabyte said they don't care about specifications, so their products are trash.
Not providing support for linux is one thing, not caring to fix their faulty products is something entirely different.