+ If the author hasn't enabled this option then there may be a reason such as a service, widget, or some other action the app will not be able to perform from the SD card. Moving the app may "break" some part of the functionality of the app. If such happens, keep in mind, the author either didn't intend for the app to be moved or never considered the option - kind requests for such an option would be a better choice.
+ Force moving the App may cause many issues with either your device or the program.
You are warned - if you don't know what you are doing, don't move the app!
Without rooting your phone (Rooting your phone can result in a very nice paperweight - you are warned!), you may be able to locate one of the file-managers or other apps on the playstore that can force move the app to your SD card - I would not d/l anything from a non-sanctioned site.