If that’s really what you were told then find different counselors. While it is often recommended since it ensures you have satisfied the GE requirements no matter what UC or CSU you end up at, it is not a requirement as implied by “need”.
I’m hoping this is just a case of you not completely understanding what the counselors are saying. When you ask them “what should I take” they will of course recommend IGETC plus major requirements but they shouldn’t be tellling you that you must take IGETC. Note, too, there is such a thing as being certified for partial IGETC meaning you fulfilled the GE requirements in some areas but not all.