I followed this tutor here and got success: https://www.youtube.com/watch?v=hE8If6gabUI.

The "Create a Windows 7 install disk" option is hidden because your system's capabilities are limited. For instance, older Macs can not boot from external USB disks, therefore creating an installer onto a USB disk would make no sense.

Still, if you want to create an installer on an external disk regardless, all you have to do is edit Boot Camp Assistant's "Info.plist" file:

> 1. Open Package content of Boot Camp Assistant app, backup `Info.plist` file somewhere, then open the old one with XCode.
> 2. Edit file:
>    - Edit section's title: `PreUSBSupportedModels` to `USBSupportedModels` (if it's already `USBSupportedModels` -> skip
> this step)
>    - Add your System's `model identifier`(Find it by `System Information` app) into `USBSupportedModels` section. 
>    - Add your `Boot ROM version` (Find by `System Information` app) to `DARequiredROMVersions` section
>    - Save.
> 3. Restart BootCamp

A comment of @dusanvf:

> If your Bootcamp crashes after this, write this into terminal:

>     sudo codesign -fs - /Applications/Utilities/Boot\ Camp\ Assistant.app/