Earlier quoted context omitted.
How many people working on Minecraft now were modders ? And how many current persons working on Minecraft are also Modders ?
The impressive part is how big modding is in minecraft despite Mojang never providing a mod interface, I don't know it may be different now but the general route for a long time was decompile the java byte code make your mod and recompile. There were a number of heroic teams that made mod interfaces out of this but a whole lot of nothing from the actual devs. I came off the quake modding scene and was a bit horrified…
And even before the source you had Quake C exposed! Quake 2 was even easier to mod.