Self reproduction is degenerative. Defects are reproduced and accumulate until the offspring are non-functional. Doesn't take long in complex critters. Non-sexual reproduction doesn't get a whole lot farther than algae and single celled critters that divide.
Some insects can do it for brief periods. Interestingly, in some insects that do self-reproduce, all offspring are male. I presume this is to assure the next generation will be mostly sexually reproduced (presuming enough sexually reproduced females to make a next generation possible).
Evolution beyond algae is heavily dependent on variability and sexual combination.