I am confused using this units. Why this changes happened?
The change never happening the lack of distinction between the two words has always been there.
Most people are not Physicists and use the words weight and mass to mean the same thing.
The word mass is hardly ever used in conversation as it is very much a technical word.
This error is reinforced by not using a word like massing instead of weighing and having spring balances calibrated in units of mass.