When you click on the link for the number of consecutive days that you have visited an SE site you see this:
However, on a fellow user profile you only see this:
It only tells you the last time they have been to the site. It doesn't even tell you how many consecutive visits they have.
I realize this might be a privacy thing, but that is a pretty lame reason. You visited the site and likely posted, too. What's the big deal if someone can see your calendar? Wouldn't be too hard to make it a setting in the preferences so that you could turn it off if you wanted.