This is the JP1 beginners forum. There's no such thing as a stupid question in here, so post away, but this forum is just for JP1 users and people considering JP1, non-JP1 users please use the appropriate forum above!
It really has to do with the default "key maps". Different device types use different sets of available buttons. Take a look at the Layout sheet in KM and you'll see the different maps by device type.