Pretty much anyone that is serious about fitness will tell you free weights are better then machines, yet machines still take up a huge chunk of gym space.
In one sense they are easier and safer to use, they keep the weight on the track it needs to be on for you, allowing you to safely do the push or the pull without worrying about it slipping, tipping, falling on you or anything else that could injure you if you lose control of it.
The trouble is you train the "big" muscles, but not the stabilization of them, which is very important in injury prevention.
Think of it like upgrading a car, if you hook the car up to a track and increase the engine power all is good and the car flies down the track. But as soon as you take it off that track you are going to be in for a crash as the steering, stabilization and breaks aren't able to cope with a much more powerful engine.
Machines can have their place, but just because a exercise is safer to do does not mean it is safer for you in the long run. Properly developing stabilization is just as important as developing strength when it comes to safe training.