1) We are used to have the toolbar at bottom.
2) This makes room for more icons.
3) It is better to lose some space horizontally because we have windows side by side horizontally, usually.
Then, why a vertical toolbar?
Unity ruined Ubuntu on my netbook because of that. Sites that I read before no longer fit in the screen width, including Ubuntu's own homepage.
I dumped that noise and installed LXDE and made my netbook usable again.
Hide Launcher: * Never * Autohide * Dodge Windows * Dodge Active Window
(the last is the default)
12.04 is currently in an 'interesting' state, so I'm waiting for the repositories to update before exploring Unity 5 on the netbook.
Did you change the default settings?