Philosophically, I think DIY gear will always be necessary for this reason:
Often it's grass roots DIY designs that inspire and motivate cottage industries to make lighter and better gear available commercially. Then, it sometimes filters down to the more conventional gear companies. This is a necessary catalyst for the overall evolution of UL. If Ray Jardine hadn't started tinkering with making his own packs, you wouldn't be able to walk into an REI and buy a Golite pack that weighs less than 2 lbs. Who knows, if DIY gear heads hadn't started putting lighter designs out there, we might all still be carrying 9 lb. external frame packs in 2008!
DIY spawns a sharing of ideas that serve as a think tank to generate new approaches to gear and overall, benefit backpackers.
Personally, I will always experiment with DIY gear because I find it rewarding and that sometimes, it fills a particular niche that isn't available commercially (yet). That's why I do it.