A lot of talk about "why" leads to the inevitable discussion about how bad Ravencrest's players are. And while it may be easy to blame the select few that are quite terrible, the simple fact of the matter is, not EVERYONE on Ravencrest sucks.
There is talent out there: every raiding guild has a few all-stars, a few who stand out above the rest.
The problem, if you'll give the expression, is that there are too many Chiefs and not enough Indians. Usually, the better players lead the raids, and given the fact that many of the people who seek the role of raid leader find it enjoyable, not enough of them want to give that up.
So what you have are guilds who are 'looking to fill a raid'; and this is when they turn to recruiting.
Unfortunately for these efforts, Ravencrest is not a young server. It has a lot of guilds that have been around since Vanilla, or even before that. Most of the raid leaders have been in guilds for years, and they don't want to leave to join someone else's raid.
Now what I am suggesting (in case you're getting ahead of yourselves!), is not to have these people suck it up and disband their raids, or leave the server to join someone else's raid anyway, but instead, choose the other alternative: co-operate.
Back in TBC, this server had a guild alliance - its name escapes me - on the Horde side. They joined a few guilds together (the Horde has always been a smaller population on Ravencrest, it was hard to put 25 man raids together back then for them), and pushed content.
I know The Firm - a guild in which I was an officer - teamed up with another guild, although its name escapes me, to clear The Eye.
These were 25-man raids too, which took a lot of co-operation and team effort to put together two different guilds.
So yes, you might have to swallow up your pride a little - you might not get guild achievements with a mixed group; is that really the only thing stopping you from raiding? But if you want to raid here on Ravencrest, you either need an existing guild raid team, or you join up with another guild and work something out together.
Who knows, in the process some new raiding guilds may form - with full rosters.