Gw dropped specialist games because they were taking sales from the main games, it's that stunning kind of logic which is applied to all their business decisions.
Mid 2000s they had a virtual monopoly in the miniatures area, they ditched popular games people still wanted to play and a host of companies moved in to take advantage.
Now the games sector is growing but gw is shrinking, they did it to themselves.
The official word I got from them after emailing them and asking why, was those games weren't turning a profit anymore. Indeed, they are the masters of shooting themselves in the foot.
As a person who used to work for GW for a long while, lots of specialist games like Mordheim, Blood Bowl, BFG, etc, were put on the backburner and in-all-but-name discontinued for one main reason: a player could collect around 10 or sometimes less models and play the game for years. To play Warhammer Fantasy or 40K, one has to buy dozens of models to barely even start the game.
Though their business decisions have been quite questionable, I tend to agree with them on this one. Why not focus on the profit generating games? The thing that was a bad decision was actively discouraging playing specialist games in their stores, because it actually alienated a good many people.
Strangely enough, Space Hulk was still paraded around quite often.