When uploading a new profile photo, the stream uses a small image to display the profile picture as seen here (second image):
Notice how the cover image stream item is much bigger than the profile photo? The profile image is an important stream item. When someone goes somewhere of great significance, this is the most likely time to show a new profile image. As a tiny image it's hard to see where the person is and what scene they are apart of. In addition to this, the profile image becomes less visible and more likely to be ignored.

Facebook knew this all too well which is why they have it use up the available space rather than a small image. At the very least we need the image to display bigger than it currently does. Just trying to make sure the best practices are being used.