Because networks tend to follow an exponential growth rate. The time it takes to go from 1 to 128 equals the same time it takes to go from 128 to 16384, so if you add 127, you've shortened the time for the network to grow from 1 to 16384 by half. Meanwhile, for a platform that already had 16384, subtracting 127 is a drop in the bucket.
> Is there any evidence that this is the case?
Facebook/Youtube/Twitter/et al couldn't have grown as much as they did as fast as they did unless that was the case.