I think I understand what you're saying, but maybe your statement was a bit too "absolute". I have been playing with a couple of lights in the 40-60 lumen range (Scorpion LED and a borrowed SF E2D) and was surprised by the incredibly wide range of uses one of those lights could handle well. If I had to own one fixed-output light for all uses then a small, high quality 40-60 lumen light would probably be the hands-down best "do everything" choice.
However, once I got out in the woods at night things changed drastically. The 50-ish lumen lights carved out an uncomfortably small hole in the darkness, and something along the lines of a stock MagCharger seemed like the absolute minimum for comfort, and somewhere around 350 lumens (MC+1160 range) was more like it.
The Mag85 provided a comforting level of overkill and while I had to admit less light would suffice it was nice being able to see all around me with ease.
Indoors, 50 lumens is ideal for navigating around a dark house in a hurry, but too bright for close-up work (blinded myself too many times) and overkill for walking quietly around without disturbing anyone.
Having said all this, I'll still agree that 50 lumens is about the perfect level if you have to pick one light and one level of output. It's just so nice that we don't have to choose