The "problem" with that is something created for isometric overview can be done less resource-intensive and less "good" looking than something you need to see closer-up, say in a 3rd person perspective.
For example the pawns of Wastelands 2 and Pillars of Eternity don't look that great, but they are good enough for the camera position faced upon them, making them more detailed is pointless since such information is not seen. However if you start looking them up real close it becomes really obvious that they are infact not that good looking. So in order to actually confirm to a 3rd over-the-shoulders view just *allowing* the camera is not enough, actual work needs to be done into making things more detailed (which can again also raise system requirements and such) or otherwise face that it just distracts from the game due to the low-poly pawns and having it there is just only giving you lower scores from magazines and dissapointed gamers since the game's unfit for that.
Something being absent is usually far better than something half-down, akwardly or broken ingame.
So no, it's not as easy as just making it an option as above poster makes it out to be.
