Are you asking in the very general sense? Of course there are reasons, both "moral" and practical.
One important one is that when courts and politicians get involved, manoeuvring in the system is more important then manoeuvring in the market. This becomes the central focus of managers. Managers without talent or experience in this area give way to managers that are.
Remember, this is not just a matter of flipping a switch. The case against Microsoft took years. During that time, the beginning of the PC revolution, the most important thing the most important company could do was win a court case and preserve a public image.
This is damage that happens so long as the system stays clean. Another problem with this sort of action is that it creates terrible incentive for corruption. Fortunes can be won or lost depending on a political decision. The owners of those fortunes will try to influence the process.
On the flip side, it isn't obvious that there is much return to this sort of "intervention." Microsoft & IBM, the two great monopolies of the computer industry both failed to do much harm. The both were clearly affected by competition. The markets stayed competitive. New products appeared. Innovation happened. They made high profits (MS still has great profits), but no obvious damage happened.
To see this at work look at telcos and other infrastructure owning companies around the world, where government intervention is usually highest. Look at the CEOs of these companies. These are guys who know how to oil the system, not lay copper wire and certainly not how to answer a customer service call. It is not uncommon for corruption to be present. Many countries have telcos owned by members of a political elite.