In general, I too would love to have unlimited BIH opportunities. On a wide open table, giving an opponent BIH can often result in a win.
However, there are certain situations in 8-ball that are much more difficult to deal with, even with BIH. Some of the scenarios below should illustrate the complexity of trying to win when your opponent is taking deliberate fouls.
One situation would be for the opponent to deliberately take an intentional foul and hit my ball into his group of balls or hit my ball or his ball into the 8-ball, thus creating a new cluster of balls where none existed before. Clusters of balls along the rails can be especially difficult to deal with.
If a cluster-busting ball isn't readily available, the classic solution to dealing with clusters is to reposition another ball from my group into the vicinity of the cluster. However, when I do that, my opponent will frequently take an intentional foul by moving my ball away from the cluster. At other times, my opponent may take a foul by intentionally pocketing my ball that's I've tried to reposition into the vicinity of the cluster. If the game is winding down and there are only a small number of balls in my group to work with, my options for repositioning a cluster busting ball into the vicinity of the cluster may suddenly become very limited.
If my ball and his ball are tied up along the rails, with BIH I may try to gently hit my ball first to separate the balls along the rails. In turn, he may then take a deliberate foul by hitting my ball into his, thus creating a cluster again.
If the 8-ball is near a pocket, and my opponent takes a deliberate foul by clustering my ball into the 8, then that situation may require extra caution to avoid pocketing the 8 by accident.
If you haven't had to deal with an opponent who frequently takes deliberate fouls, you would be amazed at the complexity of trying to overcome the obstacles these unorthodox situations present.