The following quote is from the oral history, “Powerhouse: The Untold Story of Hollywood's Creative Artists Agency” by James Andrew Miller. The speaker is Dustin Hoffman. He's talking about the work necessary to massage the script for “Tootsie” into something that Sydney Pollack would be interested in directing:

So we were finally getting somewhere. But then Sydney called and said he was very disappointed, and that Larry [Gelbart] wasn't successful enough on the draft for him to do the film. He sent me the draft and I agreed. We knew we needed a new writer, and I told my lawyer Bert Fields we were in trouble. He suggested Elaine May, and got me together with her. Elaine read the script and she was extraordinary. She hit it on the head; she understood what we were trying to do. She came up with my roommate and that the girlfriend has to have a shithead as a lover, and she has to have a kid, and a father who falls in love, and she said, “I'm telling you right now, you have to have a girl already in your life and I'm going to write her with Terri Garr in mind.” She was amazing, wrote it in three or four weeks, and that was it. Whatever was missing, we knew we could correct during shooting.

Look at all she added. That's a lot of the story. And guess what? She was uncredited. No onscreen credit. According to the above, she actually made the movie possible, and her reward was whatever they paid her and “Thanks, Toots.” Meanwhile, for decades, people have been slapping Larry Gelbart on the back. All of this for a movie about how women get screwed in the workplace. 

At least it explains why Hoffman did “Ishtar.”