If you plan on getting a PhD could you strictly take classes in your field to prove yourself and not get your bachelors? Could one potentially get into a PhD program if they don't take college graduation requirements and instead take more classes in their field?
There's no answer single to whether you can do this: every school sets its own policy, although the overwhelming majority will not allow you to apply for a PhD without a Bachelor's degree.

However, even if it is allowed, you should not do this!


A PhD involves a large amount of reading, writing, and self teaching. Taking a breadth of classes helps to hone your skills in these areas.
Real world papers are often interdisciplinary, so having a breadth of knowledge will be helpful in understanding (and writing!) these
If you have a degree and major in your subject, you will likely have enough knowledge to teach yourself things from the classes you didn't take.
Electives give you a good opportunity to take classes in things you enjoy but aren't related to your future career