One area where I can see LLPP working for us might be when we take my parents (in their 80s and not as fast as they once were) with us and our teens. We already get LLMP and sometimes have done VIP tours (though only at WDW; at DL I feel like I can do pretty well with just modify and refresh and LLMP and LLSP). LLPP in this case would allow my parents to take the day as slowly as they need to, and to spend less time walking across the parks to get to rides. We could just go in the order of geography, and stop to rest or do shows or eat whenever it was needed, rather than on the LL schedule. As well, selfishly for ME, it would let me not be constantly on my phone, trying to modify LL times to minimize park crisscrossing or park hopping. I would be thrilled to be more present on our park days, not worrying all the time about trying to optimize the LL times to minimize walking.
So if I ever get the joy of having my parents back in the parks with us and our daughters, I would consider this. We usually only go 3 days, so maybe we would do this one of the days.