I totally disagree. Matsuoka was left writhing in pain on the court, even after being defaulted, because his cramps were treated as his own fault. Eventually, he was attended to. You don't know that players are "abusing" the rule at all. That's nothing more than a personal belief.
When players take MTOs on other player's serves, during key moments in a match, don't ever take them when they're ahead, come on, it is just common sense.
If there is a loophole that can be abused, there are going to be unscrupulous players who will abuse it.
Irrelevant of what you think, the opportunity for abuse exists. A game penalty would counteract that, and is completely appropriate.