Becuase the first person pronoun for the subject is "I" and for the object is "me."
I went to the store. Mom and I went to the store. I am the subject in the first, and Mom and I are the subjects.
Please send copies of our vacation photos to ME. Please send copies of our vacation photos to Mom and ME. The indirect object is me in the first, and Mom and me in the second.
He accidentally hit ME with a badly thrown pitch. He accidentally hit both Peter and ME with badly thrown pitches in two different innings. The direct object is me in the first, and Peter and me in the second.
I accidentally hit him with a badly thrown pitch. My mom did the same thing thirty years ago when she was in high school. Both mom and I have hit people by accident while playing softball. In these sentences, Mom and I are back to being the subjects.
Also, you put the other person first "Mom and I" not "I and Mom."