I considered doing that, but the bonuses and other gains in Ethics make it worth the trouble for me.
For examples, there are diplo, morale, and mil production bonuses, and the chance to build the MCC and No Mercy Invasion buildings, also.
In DA, the MCC presents an unintended dilemma. On one hand, you get a 100% econ bonus. On the other hand, you'll never influence flip a planet again. A couple years ago, I did an gamey tactic with the MCC. As soon as I had several Major AI planets showing the unhappy symbol, I evacuated the MCC planet of all but one colonist, picked a Minor deep within my borders, and gifted that planet to them.
In a few turns, all the unhappy planets flipped to me, I bought/traded back the low-pop MCC planet, and repeated the process a dozen turns later, and so on.