Japanese Jujutsu in its original form was all about using grappling techniques when necessary to mainly ground an armour clad enemy and control them long enough to access your weapon to finish them.
The holds were never intended to 'submit'. 'Tap outs' were only devised much later for sporting contest. Ground holds as we know them today did not exist until after the reign of the sword disappeared and Japan became more westernised and wished to preserve some of their Martial arts history abet being some what watered down from their original forms.
Back in times of war or conflict going completely to the ground would get you killed in a real encounter as most people were armed. Unarmed combat was certainly not their first option.
The main intentions of finishing holds in Combative jujutsu were; A. To control an enemy long enough to administer a killing stroke with a blade. B. Break their weapon arm so they could not use their weapon. C.Last resort was if they could not assess their weapon or turn their enemy's against them then they would use a choke or strangle to finish them.
Striking wasn't really relevant at this point in jujutsu as the wearing of armour rendered it ineffective. Samurai were great swordsmen but were expert mounted bowmen first. Some say the origins of leglocks developed from bowmen being dragged from their horses and having their ankles or knees broken so they could no longer re -mount and were now vulnerable for the kill.
If you look at the image above and imagine a blade in my hand you can get an idea of how these holds worked. Hundreds of years later many of these holds were adapted by law enforcement to restrain,tie or cuff a person taking on a whole new purpose. Jujutsu today is just another re -birth of an art that has been around 2500 years plus and has had more re-inventions than Madonna. Remember today's participants you did not invent the wheel. To appreciate the jujutsu of today sometimes you need to also revisit the pass and learn its lessons