The same reasons why many people find any kind math difficult, They are afraid of AND they do NOT see HOW the calculus or math APPLIES to REAL LIFE situations.. They may also have dyslexia or synesthesia or spatial perception problems.. I get the number order of four digits mixed up.. Try taking calculus course for NON-science majors and see how much more work AND TIME there is adding up the areas of all those little boxes than it takes to differentiate an equation like y = x + !0v+5a + 43, then calculus might make sense to you.
i used to hate and despise math until i turned it into personal challenge, a puzzle i knew i could solve IF I HAVE ENOUGH TIME. Just don't make me take a timed math test with a bunch of engineering students, because i have taken AND PASSED 5 semesters of calculus. i probably still have chronic math testing anxiety. anxiety and panic attacks when my mind goes balnk in the middle of test.. Walk out of the test and the rest of an answer to one question pops back into my head..
I thought i was dumb and stupid in math too, until i realized My SAT scores indicated i wasn't COMPLETELY dumb and stupid in math..
It's a kind of self fulfilling prophecy, if you think you are dumb and stupid and cannot understand something you MIGHT be that way for the rest of your life.. My father helped a lot in high school, until i took calculus my senior year of high school, which was the normal senior math course. i had to take it to graduate from high school. He admitted i was beyond where he could help me. He never went beyond Algebra 2 in high school, and he had biology Ph.D, M.S. B.S college degrees. He did the family account books and taxes until his death.. My mother had her own bank accounts and and taught me a lot about interest and banking fiance. BOTH my parents were alive and and survived the Great Depression and the dust Bowl...
WHY are so many college students so afraid of GETTING A TUTOR., Yes, you are lucky if you can find A GOOD tutor who can explain things in terms you understand,, but at some point you MIGHT be able to "connect the dots" and "see " HOW the math equations apply to real life situations.. THAT is when math, including calculus, starts to "make sense." you may not make A's in math classes, but at least you UNDERSTAND SOME of it.