Probably one of two things:
b) the perception that it’s hard
b) the perception that it’s boring
It’s my opinion that neither are true!
a) Everyone has different skills- if you’ve got a curious mind and you’re keen to find out more about how the world works then it doesn’t really matter what your grades are like- you’ve got everything you need to work in science in one field or another!
b) I’m the first person to admit that I didn’t enjoy every single science lesson when I was at school- some were really dull! But science in the real world is not about remembering facts- it’s about using your skills to discover unknowns and I think that’s pretty exciting!
Being a scientist isn’t for everyone, and that’s fine. But I’d encourage students with an interest in science to keep their options open for as long as they can, and who knows, maybe they will be sitting here talking to students about working in science one day 🙂