Most of the top players now want to win points with their forehand. When they are close to the table the backhand to backhand rallies are usually because the players are usually too scared to give it to their opponent's forehand.
This is not completely true, though it has some validity, and was more valid before the development of modern backhand techniques. Like you said, the problem is that you cannot change direction with a weak ball and that the forehand is generally more powerful than the backhand.
That said, a number of world champions and even Wang Hao before Zhang Jike dominated on the basis of their ability to dominate the backhand diagonal of the table. Like them, some players have learned to just dominate that diagonal with superior backhand play, blocking and even a pivot strategy. Also improved backhand pushing to the backhand (Waldner) because backhand openings are generally less vicious than forehand openings even if sometimes tremendously spinny. Or even go to the middle and then to wide backhand off a weak ball. But the real revolution was the realization that you can attack serves much more easily with the backhand than the forehand. That made it harder to serve to modern backhands.
In the end, table tennis is partly about being able to pick poisons and set up matchups to exploit. The guys who go backhand to backhand are not trying to avoid your forehand anymore. They are trying to pursue one of many winning strategies.