people shift between services like github and bitbucket and alternatives all the time. Perhaps not often on an individual basis, but at any one time many people are deciding where to put their stuff.

Almost anything that gets the name of a particular service bumped up to the top of someone's consciousness for a little while will shift some of those decisions toward that service.

This is why even the world's most popular brands (Apple, Coke, etc) never stop spending money on marketing / PR :)