[pfdietz]

Uh huh. How long was PV emerging before it crossed a threshold and took off? PV was invented in 1946 (exactly when is debatable; it could be said to have been earlier) and didn't explode until about 2010 (if not later).

So your observation doesn't excuse the non sequitur. Things have low adoption until they don't (if they ever do). This doesn't mean they will necessarily take off, only that the observation that they haven't yet can't by itself be used to conclude they never will.