Why isn't off-the-ball hack-a-Shaq totally illegal?

[Direckshun]

I was watching the Spurs play the Suns last month, and late in the game they just sent guys at O'Neal to foul him, even if he wasn't even on the offensive half of the court yet. Shaq would juke and boogy, trying to get away from them. It was every bit as ridiculous as it sounds.

I thought there was some sort of rule there, and today I run across this on Wikipedia, talking about Wilt Chamberlain:

This led to the spectacle of virtually an entire other contest being held away from the ball and almost completely outside of the basketball game being played, as Chamberlain essentially played a de facto game of tag with defenders, attempting to run from and dodge them as they chased him trying to foul him.

The NBA decided to address this undesirable situation by instituting a new rule regarding off-the-ball fouls — that is, committing a personal foul against an offensive player who neither has the ball nor is making an effort to obtain it. The new rule stated that if the defensive team commits an off-the-ball foul within the last two minutes of the game, the offensive team would be allowed to keep possession of the ball after the awarding of either one or two free throws.

Why only the last two minutes? Isn't this tactic ridiculous at any time?