If your fitness goal is to lift heavy weights, then sure, these may be the only exercises you need. But if your fitness goal is to freeclimb a sheer rockface, o

If your fitness goal is to lift heavy weights, then sure, these may be the only exercises you need. But if your fitness goal is to freeclimb a sheer rockface, or dunk a basketball, or run a 7-minute mile, or be a great skier, then they probably aren't enough, and may actually be detrimental to those other goals if you overdo them. People go to the gym for a variety of reasons, and pure strength is only one of them.