Well, yes... But is there any reason why our laws should say so?

I don't think you're understanding the conversation, so let me make it simple for you. In the above posts anywhere you see where it states "DG I", read it as Demogame 1.
Be gentle with the newcomers!

Wait, you're both newcomers...
No, the question is why would we
want polls to be public.
Early DG's, on Civ3, had an interesting feature. One or two elections during each term would have a vote total way above all the others, sometimes approaching more votes than we had citizens registered. I won't speculate on why, there are a few references to this in the archives if you really want to go hunting for it. Simply put, there were some citizens who were worried that outlanders were voting in our polls.
When public polls were added to the forum, the DG immediately adopted them as standard, to avoid the feelings of vote fraud that people had. Since then the membership group was added, so it's impossible to vote without having been vetted by a mod or group manager, so public polls aren't really needed any more for the fraud prevention purpose.
A second reason for using a public poll is to see if people are talking one way and voting another. This is useful if you're new to the game and still learning who you can trust and who you can't. It also provides political material should you end up in an election with someone who always does that.
A RL analogue to justify public polls is that we're like the congress for the people of the civ we're playing. Congressional votes are recorded so the people know how their representative voted. Some of us want the candidate's voting record at election time.
That was kinda long, but we have a long history.
