Because we still can't define what intelligence is.
Just imagine what the human mind's distributed representation of the "intelligence" concept would look like. Clever animate entities (and most associations therewith) are way off in their own private corner of vector space compared to just about everything else.
When the gap is this large, the enormous void in between somehow becomes a non-object (to superficial cognition) and so people just begin to presume that we need to jump the gap, rather than slowly filling the gap in.
It's almost like the travelling moon illusion when you're driving in a car and the moon is low in the sky, off to the side (which children find amazing, but adults have learned to ignore).
I was thinking about the sun this morning and about relative illumination at different latitudes. The correct physical model is parallel rays, which immediately suggests that for a perfect sphere, the poles get no direct radiation at all during equinox, the eternal kiss of sunrise=sunset.
Then I looked outside through the window, and realized that the human brain—which knows the sun is far away—still doesn't think it's as far away as the earth is wide (very wide, if you believe in a flat earth model) or even a few multiples (but it's actually thousands), and so the intuition from our eyes never says parallel rays.
We've been nibbling away at the giant AI void quite successfully, but the travelling moon illusion still makes us think we need to jump.
The reason we keep reclassifying our victories as "not really AI" is because we know for a moon fact that the void never actually changes size. But it does, and it has, and it will continue to shrink, and I really don't think we're going to spring generalized intelligence all at once out of scary clown box.
First we must learn to perceive the void as a continuum of many way points, mapped out by many generations of technical improvement, like Vancouver and Cook or Lewis and Clark.
For me, recent results with LSTMs have made the void seem just a little bit smaller than it was before. I'm now at the very beginning of an ability to perceive the moon as being at a great, yet finite distance.
With something so thoroughly hived off in its own corner of distributed-representation hyperspace as intelligence, what's to define, anyway? Definitions are street signs erected in conurbia, which one resorts to after Toronto and Hamilton and Niagara Falls have all become built-structure indistinguishable as you skirt the horseshoe.
There are many conurbations in distributed-representation vector space where definitions are the last gasp at forestalling cognitive Gangs of New York. Definitions are less important under open skies of Boise, Idaho or Butte, Montana; even less important still when you've wandered out into the green grid-lines of the entirely unpainted Matrix.
Here's a quick test: if your frontier town's "population #,### sign" (there is only one sign) and it has at most one comma, definitions are premature.