Because that is a very important piece of information which users are likely to expect or to even look for when invoking a tooltip.
PS I'm slightly concerned about lowercase "… connected" and uppercase "%1% Battery". Is it OK?
but one of them is without battery info
Note: frameworks/bluez-qt!32 (merged) is needed for this to work, but not strictly required in a sense that the code wouldn't break — just won't show you battery info.