You are born. You train. You compete. At some point your body cant compete any more, for whatever reason. Time to stop.
In my puny mind... it really is that simple.
It isn't as simple as they have the same level of testosterone so it is fair. They have years of experience and training over the younger guys. Fresher more athletic and quicker recovering bodies are the advantages of youth and experience and knowledge are the advantages of being older. This alters that in a completely unfair way and for the most part is being exploited by people who spent their youth abusing steroids to gain similarly unfair advantages over their competitors.