Tip up seems like a good idea if the knife is secure somehow. Although I don't do it, tip up on a shoulder strap could more easily be made faster to deploy.

I do see a need to access a knife quickly. As one of many examples, you're walking and some weed/twine gets wrapped around your legs, holding you. I personally would not want to spend 30 seconds brute forcing my way out or fumbling for my knife. I'd rather deploy my knife quickly and get out as soon as possible. There are many other examples in which I'd want quick access to my knife.