Obviously not the OP. Another common reason is that a good number of countries do not allow dual citizenship. So you'd have to give up your "original" citizenship...

Not so much for tax reasons - because permanent residents are generally subject to the same taxes as citizens - but for estate planning purposes,

That is why i said future tax. Like you hit it big, and wouldnt want to deal with renouncing your citizenship.

Otherwise you dont really need to be a perm resident. Being resident for tax purposes is sufficient.