INVITATION ETIQUETE

Recently I was invited to a wedding, we received the invitation at our home so they do have our mailing address. We go to my in-laws house and she received a shower invitation for the same person with my name and my sister-in-law`s name added to the envelope. They have our address for the wedding invite - why don`t they send us our own shower invite. This is really a pet peeve of mine. If you want me to come to your party (and bring a gift of course) send the invite to me!!! Am I wrong thinking this?