For those of you that work in non-teaching field...how would your boss ever know what grades you got?
Teachers have to show our transcripts.
most bosses wouldn't have any idea - however in many fields good (and sometimes elite) grades are required to advance along the path toward some professions
many jobs require post grad work - you simply are not going to get the opportunity to do grad work (get into grad school - phD programs - professional school) without very good grades
likewise many jobs right out of college require letters of rec - those with better grades I would think tend to have better recommendations
many selective engineering programs require elite grades in high school to even enroll in the program -
nursing school is extremely competitive and gpa (fair or not) is a common litmus test for narrowing the selection process
maybe a student with a 2.5 gpa would make just as good a physician as someone with a 3.8 gpa - but you will never know because few if any with a 2.5 gpa will ever get the chance
lastly many college students enter college without knowing the specific career path they want to follow - those that finish their first year with low grades greatly reduce their future options of career choices