If you have ever had the “pleasure” of being called up for jury duty then you will quickly see that anyone thought to have more than half a brain still functioning is excluded. I have been called up several times and been thrown off as soon as my title was noted (not that having a Ph.D means you have half a functioning brain).
Addendum to the why:
- If you lean towards one side, the other side is incentivized to dismiss you.
- If you're in a case with lawyers, both sides actually want jurors that they can influence, rather than jurors that will come to their own, unexpected, uncontrollable conclusions. That would be a dangerous wildcard.