Regrading grabs in Aikido...
A while ago I showed my Father Ushiro ryokatadori Kotegashi. Afterwards he claimed that nobody would ever bother to grab you in such a way as Ushiro ryokatadori. I thought about it abit and decided to ask here: Just why exactly would grab you from behind by the shoulders or wrists? (e.g Ushiro Tekubitori).
I've seen more realistic grabs such as Kakaedori online, but for some reason my dojo doesn't practise them. (Atleast not during the duration I've spent there)