I would agree with you, up to a point. I agree that one doesn't need to put oneself under undue strain every time in the gym, and you can get a good workout from doing lots of reps for light weights.

But naturally by virtue of not increasing the weight on the bar one will reach a point where one ceases to get stronger (measured by the amount of force you can produce). There are limits to what more reps will do for you.

So don't deadlift your 1RM every time you go to the gym, just slowly increase how much you lift in a safe and structured manner.