Almost all the graduates and post graduate students I had come across did copy and paste (mindless lefting) when writing their projects or research thesis....why is it so?

There will always be room for copy and paste irrespectice of the project topic. Adequate referencing is what matters and beside ur project must have been researched by someone before so copying and pasting that person's write ups is not a sin so far there is adequate sighting referencing.

The main word is PLAGIARISM.