That's because most who coach at that level don't know the rule's well at all. Believing that a balk is caused from illegal action by the pitcher only.

On an IBB it IS an illegal action by the pitcher - at least in OBR.

8.05 If there is a runner, or runners, it is a balk when—

(l) The pitcher, while giving an intentional base on balls, pitches when the catcher is not in the catcher’s box;

The catcher created a situation where the pitcher could balk, but it is the pitcher that continued with the IBB and actually balked.

There IS one action by the catcher that is beyond the pitcher's control and results in a balk call - see 7.07.

Yes, the pitcher gets dinged for both not knowing the rule and having a catcher and quite possibly a coach that also doesn't know the rule and teaches this. I'll try in the future to make myself clearer for those anal retentative in the forum.