You ABSOLUTELY POSITIVELY DO NOT NEED TO BE CERTIFIED BY ANYONE in order to get and do shops. I am not certified, have not been certified and have no intention of getting certified yet I get shops offered that are as good as or better than gold certified friends of similar experience. Without certification I have done $400 shops. Without certification this month I have done a $78 dollar shop.
Even the MSPA indicates in their notes about shops that "the certification may give you an edge with some companies. Imagine two shoppers in the same town, with the same experience and work performance. One is certified and one is not. All other things being equal, the certification sets one shopper above the other with some companies."
While there are or may be some companies or schedulers who give preference to certified shoppers I think even they recognize that being certified does NOT guarantee doing a good job. Earn your reputation by the quality of work you do and you will be finding and getting offered jobs.