Let's think about what actually happens when you ban public officials from trading stocks. The goal is preventing conflicts of interest, sure, but you're treating the symptom while ignoring the system that creates the conflict. If an official can't buy individual stocks, they'll just park money in index funds or real estate or other assets that are just as affected by policy decisions. The conflict doesn't disappear, it just becomes less visible and harder to track.
Meanwhile, you're pushing talented people out of public service. The people best equipped to make sound economic policy are often the ones with investment experience. Telling them they have to liquidate everything to serve is a huge deterrent. You end up with a government of people who are either wealthy enough not to care or too inexperienced to understand markets. That's a feedback loop that hurts everyone.
Better approach? Strong disclosure rules, recusal from specific decisions, and real enforcement. That addresses the actual problem without throwing the baby out with the bathwater.