Because either (A) they aren't buried all the way back to the substation. or (B) you lost a transformer somewhere along the way

I see everyone clamoring to have underground wires so they won't lose power all the time and it does make sense. But can someone explain to me why I am still without power even though my neighborhood has underground cables? The majority of my neighborhood had their power back on by yesterday but there are still a few streets without.

So why do underground cables lose power too? Please someone explain how it all works!