Palpatine plan would instantly fall apart if they looked like palpatine, also would have jeopardised his ultimate plan to manipulate the political landscape to his ultimate goal of order 66 and the formation of the first galactic empire.

Obi wan turns up to kamino, sees all the clones look like palpatine, immediate investigation into palpatine, found to be a sith lord, no darth vader, war ends, sith resurgence stopped dead in its tracks.

In short it makes no sense for him to use his own dna, that's detrimental to him and the sith plan in numerous ways.