The original Commodore PET was the first ready-to-use home computer, the Sharp copied the form factor.
And on the note of ergonomics, the offset keyboard is better IMHO because from the home keys you can easily reach the two above and the two below with minimal finger movement. With a "straight" keyboard, you can reach one key above and one below marginally easier, but the keys to side involve much more lateral movement. The finger joint doing all the aiming work is a ball joint, so using offset keys is more natural.
I'm just surprised they didn;t decide to go for broke and get rid of the whole QWERTY idea at the same time!
 Other language specific QWERTY-alike layouts are available.