Why is mass more useful than weight for measuring matter

Q:
Why is mass more useful than weight for measuring matter?
A:
Mass is a basic property of a given object, whereas weight is actually variable throughout the universe because it is actually a measure of the force exerted by a given object and not a property of the object itself.
Weight, unlike mass, is a function of both gravity and mass; that is, an increase in mass will cause a corresponding increase in weight if it is placed within a gravitational field.
However, a given object's weight will vary from place to place (namely from planet to planet or within a spinning centrifuge) because of the effects of gravity. Mass, on the other hand, is independent of gravity. Thus, three grams on Earth can be considered the same as three grams on the moon or on Jupiter or in the vacuum of space. Imagine weight were used to measure the amount of matter. If this were so, all objects in space would appear to contain the same amount of matter because they all had an apparent weight of zero. Using mass as a metric instead, one can differentiate objects in space from one another by the amount of matter that they contain (their mass). 
https://pippagoldenberg.wordpress.com/2010/11/26/weight-and-centrifugal-force/

https://www.nyu.edu/pages/mathmol/textbook/weightvmass.html