Scroggins said in an interview and confirmed by other lefties that on today's tour patterns, for the past few years if you wanted to cash or make shows as a lefty that you had to become a master of playing outside 5 because that is the only place a lefty is guaranteed to find head oil on the burn squads on tour.
As someone posted above, when the righties are forced to loft the gutter, the lefty head oil is gone from about the 6-7 board in on the late squads.
That's why when the lefties make a show, they play the gutter because that's where they have played all week.
The only way this will ever change in this discussion, if for someone to either develop a lane conditioner that a bowling ball cannot remove from the lane and thus you are forced to play the pattern or someone tries to develop patterns that have so much head oil, that it will hold up thru 8 game blocks and again you are forced to play the pattern.
I don't think either of those will happen any time soon. But that would be the perfect solution. For example: if the bowlers could not modify the pattern with their equipment, a tournament director could create a pattern that forced the righties to play up 5 and it would never dry out. When is the last time, that ever happened? Both sides would have the same shot and it would never change. That is the ideal solution that will never happen anytime soon.
But I think that is the goal. The new Ice oil by Kegel is a step in that direction and bowlers have noticed that when their lanes change to that oil, the patterns last longer before transitioning.