PA Control the number of Servers because they want to balance the number of players vs server to enourage some form of PVP via contest in spots (Gathering or Grind). At it's core, BDO is a mmo with PVP element and they intend to keep it this way.  Too many servers, and people will have no need to contest for resource and thus, no need to PVP for anything. 

That is a good reply, but we see NA / EU people can just transfer to any of their 30 servers and grind Stars End. So the argument that they want to keep PVP element alive seems to only be applicable to SEA server.  

I think server count is also based on projected population. NA has more servers, biggest there are more people who might potentially play, compared to the SEA region. But there is no official response to this question yet.