Because grammar is about improving writing. And passing the test is a by product of good grammar teaching.
Because grammar will be boring for those who have to put up with 2, 3, 4, 5 or 6 years of this.
Because grammar should be fun.
Because grammar teaching should take place in context with authentic texts and discussion about the impact.
Because preparation for the test is important but only needs 3 or 4 weeks.
Because if we don’t hold on to what is important in grammar teaching, no one else will.