The base grinding makes them much less likely to cut hands on the base when using them. The “ears” behind the notches are exposed when they are hafted. While one would only have to dull the ears, that is actually significantly more difficult to do than just dulling the entire base. I suspect knife blades that were not base ground were hafted or used in a way that kept the sharp edges from cutting the hands.
Fluted points (dalton, clovis) are dulled (aka “basal ground”) up the sides a ways. Which is why I suspect they were hafted with a pinch/compression system rather than wrapped with sinew. I used to think the sides were dulled to keep from cutting the sinew wrapping, but after hafting and using many knives and arrow points, I realized that the sinew does not cut on sharp edges. It dries to a hard casing and unless a sawing action is applied the sinew not only wont be cut by the edge, it will do the job of protecting ones hand from the sharp edge. Actually sinew wrapping holds more securely on a sharp edge than a dulled edge! My favorite ever way to haft a clovis is to split a handle shaped piece of wood, or just a stick about the right size, then tightly wrap some plant fiber cordage around the two halves behind the blade which is sandwiched between the two halves. Then take a small wooden wedge and shove it in between the sticks at the butt of the handle. This clamps the blade tightly, and those ridges on the sides of the flutes dig in to the handle wood and hold the blade very securely - like securely enough to get to work cutting up big game and such. And then, when finished using it, I would just pull the wedge, blade falls out, and put all the pieces in a small bag for storage/travel. Its a sweet little takedown knife system, and you always have a length of cordage if you need it for something other than the knife handle. So there is a dose of free and unsolicited archaeological interpretation.