You're ignoring the primary (marketed) purpose of these extensions - social sharing. The main value-add is that users can easily +1 (share, tweet, whatever) from whatever page they're on. A secondary feature of some (including this one) is to show how many other people +1'd (etc) it. There are other extensions that exist with just the first part and not the second (though they're usually not 'official') and I imagine those wouldn't be "tracking" your activity (except what you're sharing). But, tracking isn't really the main point anyway. Facebook and Google can do enough tracking without browser extensions simply through market saturation. As far as I see it, this extension just provides features that some users want.
Additionally, these extensions take up minimal space in Chrome. The screen real estate each one gets is the same size as the settings (wrench) icon. Sure, you could fill up your browser UI space with them, but it's much more difficult than it is with IE and there are more hoops to jump through in order to get them there. IE users were (are?) plagued by toolbars because they can be installed externally from the application. As far as I know, Chrome extensions can only be installed from within the application after several prompts and confirmations.
The tracking should ocurr when the user performs the +1.
It shouldn't track the way it does, and it certainly shouldn't track HTTPS. It is not even an issue of privacy, it is simple courtesy and common sense.
Here's a happy medium: track it "on demand". Let's say, when you hover the mouse over it.
Or make the +1 a two-gesture event: click the extension button (which is when "tracking" occurs) which opens a balloon, then click a +1 button within the balloon.
If the extension doesn't send the URL to Google anyway, then it can't know how many +1s the page already has (and from whom). That's why it triggers on every page load.
You're missing the point - Google knows how many +1s the page received. But the user's browser doesn't, so it can't display the +1 count without contacting the server (and sending the page URL) to find out.
I have to wonder if this is an unintended side effect of the recent push to have site move to HTTPS - it used to be that HTTPS requests were mostly unique to a user, but now lots of "regular" pages are being requested using HTTP and if you want to make any kind of extension that return data about pages (+1, anti-phishing, etc) you're probably going to to want to send HTTPS URLS as well.
Additionally, these extensions take up minimal space in Chrome. The screen real estate each one gets is the same size as the settings (wrench) icon. Sure, you could fill up your browser UI space with them, but it's much more difficult than it is with IE and there are more hoops to jump through in order to get them there. IE users were (are?) plagued by toolbars because they can be installed externally from the application. As far as I know, Chrome extensions can only be installed from within the application after several prompts and confirmations.