If you look at the concepts of posters he's done, and what the final product ended up being, it shows that directors or studios want the same vanilla Struzan. Everybody wants the same Photorealistic collage. Even the people they hire as his copies go with the same formula.

Nobody's asking for stuff like this anymore. When you see his scraps, he'll try something like that, and it will get turned down in favor of the collage look:

Here's people trying to do Struzan's style:

Struzan has sort of been turned into the AC/DC of the art world. If he tried to do anything different, people wouldn't like it at this point. It's probably the reason he's retired.