Was that pebble to close to a vital organ to remove? Bike evolution being the way it is, dictates that if the belt was truly better all bikes would have it. How many are sporting the belt? Mostly cruisers? If you are the type of rider that may dissolve in oil it's a must have.
The pebble was bulging out but not hitting anything. Since it was in the middle of the wide belt, it was not a structural issue. If it were near to the edge the belt likely would likely to have needing replacing.
Why don't all motorcycles have belts? For sportbikes, maybe their power output causes undue strain on belts. I would think the Enfields would be prime candidates for belts, except that they wouldn't fit the tradition, and would look out of place. Witness the Buell Blast belt and rear "sprocket".
But didn't the first motorcycles have leather belts? That's a tradition I wouldn't want to explore!