I agree than with weapons and multiples etc that ground fighting isn't a good idea but it's not new look at ancient Greece they had boxing and wrestling probably before bodiharma went to india in fact I think fighting arts went from there to india for they did trade but thats another discussion in it self.
However with weapons if you take somebody down and are in top position with a blade I'd say hit should be quite easy to finish one and move on to the next?
From this I'd say escapes and some other bottom techniques evolved however when training soldiers with limited amounts of time then why get into this?
This is just why I don't think ground fighting is touched in so many arts not that they are incomplete and I'm not disrespecting them it's just the quick path to battle readiness that has been passed down from generation to generation.
Like a formation of soldiers keeps its intervals and cover in line formation as they move in (lets leave guns out of this) if one wrestles on the ground that makes a weak point in the line so perhaps also for this reason wrestling wasn't toughed as well. who knows????