I remember, on virtually every installation of Windows XP, I had to go hunting for the config that showed the volume icon. This was quite frustrating to me, and although the issue is quite old, I would like to know why they did this! It doesn't seem very user friendly to me.
From Microsoft's own support page:
This was a break in previous versions of Windows, and I don't believe they have repeated it in newer versions (although they removed the whole start menu in Windows 8!) So:
Why was this turned off by default on Windows XP installations?