All it takes is one fallen power line or tree to turn that stroad into a giant parking lot of death. Cutting back brush and undergrounding power lines is much more cost-effective than building stroads up into the hillsides.
"The utility says more than 30 power poles are down in West Maui, including along the Honoapiilani Highway at the south end of Lahaina." (That Highway aka Highway 30) was the main southern route out of town.)
"A telephone pole falls behind their car, causing an accident and blocking a side street."
Everyone living in an area needs enough space to evacuate fast enough to get away from natural disasters safely. It doesn't matter if there's a downed power line when no one can get out due to gridlock even in the best case scenario. Everyone's gotta be able to get out fast enough.