> What troubles do they cause?

Once, a colleague working on Linux created two files with same name but different case, and committed them to the Git repo, and then I tried pulling it on my Mac. I don't remember exactly what happened next, but I wasted a lot of time trying to sort that mess out.

(There was no real reason for them doing this, it was just a mistake on their part, and they didn't notice they'd done it before committing the files.)