Question about phrasing

I allowed myself to graduate from Chapter 1 of the Anniversary Manual last weekend :-), and I hope someone will help me with a question about phrasing..
They phrase I-am and I-have, but not I-go.  This would seem to be a logical phrasing choice, and I don't understand why it isn't done.  One of the things I like about the Anniversary Manual as opposed to the later systems is that most of the rules are pretty explicitly states, but I've missed this one.

(by john19970 for everyone)