Bulbs still make sense to a lot of people because they are a user-serviceable format -meaning the user can screw in a new bulb when the time comes. LED, on the there hand, still requires a level of understanding that goes beyond screwing in a lightbulb. That and the up-front expense to get a good LED fixture are two things that keep people from converting.
Another thing that comes to mind is that bulbs can be purchased in different spectrums. If a new bulb comes out that is in a color that a grower prefers, it can screw into an existing fixture and that's that....done deal. So, those people are basically buying into a format that doesn't alienate them.
Maybe there's more people out there, like me, who watch new LED stuff coming out, get excited about it, get the wallet out to buy into it.....aaaannnnd then something new and better comes along the very next month!
I'm really in a holding pattern at the moment to see which new technology will be the "cream" that rises to the surface. Seems like there's at least three, distinct schools, now: The HID bulb guys, The LED COB guys and the Samsung chip guys....and now the new "hybrid" technology! I'm sure they'd all work well in the right hands. So...What's it gonna be? One? All?