Because these M2000 are becoming older and older.If Mirage2k they using are that much advancedd, why UAE is selling it & going for Rafales? Also remembere UAE is not facing any threat as we facing now. A nuclear armed nation with highly skilled military personals, arguably the best military in muslim world is threatening us from western border and a super power with exotic weapons is grabbing our land from East.
Also,There is no room for Mk1a & second hand Mirage, save that money and & go for more Rafale.
Because the foe neighbor Qatar have purchased a wide fleet of modern fighters.
Because UAE have no money problem.
Because....