Guild Wars 2

Can anyone explain to me why certain sigils or runes are soulbound to the character.

The affected runes include, nobel, golemancer and more and there is nothing hugely unique about the sets to set them to force them soulbound only. It is nearly impossible for a player to aquire a whole set this way and it is even a searchable function on the auction house.

I am unaware if this is a bug however it seems as if they have been directly set this way for some reason, could someone please enlighten me.

If you do dungeons, you most likely got the rune/sigil from the chest which in turn makes the rune/sigil soulbound.

Dungeons are not the only way to gain these runes, it seems counter productive that people should need to farm dungeons just to get a set of runes that they desire.