Because BN is good at playing politic..Opposition is still noob. If you noticed, bn likes to play good cop,bad cop game,especially in Sarawak.. Bn Sarawak(pbb) will be painted as a good cop defending the Sarawak right against federal government..
Another thing is, BN has a large resource and good local machinery to serve in rural area.. Even in remote location, there will be a PBB/umno/bn branch.. These branches will be manned by that party members.. Opposition just don't have this kind of machinery..
Why Sabah Sarawak keep supporting BN?