horse trotting with tight shoulders

Question
hello ma'am, why do few horses trot with tight shoulders. what does it mean?

Answer
I am not sure exactly what you mean by "tight shoulders"?

Do you mean from comformation, that the movement is not free and forward?
If that is what you mean, that is why the way horses are built, (their conformation) is so important. If they have a straight shoulder they will not have the movement and reach necessary for racing, jumping, dressage, etc.

Of course lamenesses, poorly fitting saddles and poor riders can also contribute to lack of movement for the horse. There are some breeds that have been specifically bred for pulling, (draft horses), and cart work, and they will often have tighter movement.