This happens in IT too. I worked for a company where I got placed through a consultancy. The direct hires had employee badges with the term "employee" printed on them, while we had ID cards with the word "contractor" printed on it.

We were never involved in internal discussions and kept out of most "employee only" meetings. We were also not called for a majority of the team building outings the company took their employees to at various resorts and campgrounds. We were excluded from the interal employees mailing list as well.

While all of this did foster a greater sense of togetherness within us the contractors, it made us feel ostracized by the larger organization itself. The place which we worked for, and the place where climbing the ladders actually meant something.