Your argument seems to be that those in public service should only survive on their salaries, because "doing it for the people" is enough of a reward that they don't need to worry about such trivialities as money.

There's no good reason to stop anyone from owning stocks. It's part of any sensible person's retirement strategy. The issue is whether there's a conflict of interest there, and blind trusts or broad market ETFs are two good ways of addressing that issue.

Other alternatives include announcing their intention to trade in specific stocks several months in advance of doing so, so that even if they know about specific long-term future advantages a company might have, it's public knowledge and others can also trade in a similar way. But the easiest solutions by far are blind trusts and broad market ETFs.