Bo1 is also entirely dependent on the map selections as well. Like Toffee said they can go so easily to one side.
Thats why the popular format in Bo3 would be 2 team based maps like Overpass or Train, then finishing with Inferno etc. A map that is cleanly winnable from both sides.
Bo1 format is also just uninteresting to watch. Take the recent C9 vs SK in yesterdays NA tourny (idk name), SK picked a shit strat then c9 snowballed, uninteresting.