Bad Putting

Very often I heard friend blaming on bad putting. Very often a bad score is the result of too many putts, as acclaimed. He concentrated on improvement on putters and putting more than anything else. However, when asked how the irons and tee shots were, these are usually quite satisfying in comparison.

If tee shots are good from driving, it will result an easy condition for 2nd or approach shots.
If irons shots are good approaching the green, it will result a good putt if the little white ball is only 3 feet away from the hole.

Question is how could there be bad putting if approach shots are good? Usually it is bad approach shot that result in a difficult putt on the green.

I think my friend will have a hard time improving his putting.