I've seen sheath knives on pack straps -- handle down/ tip up ( usually on the lift side). I've tried, but I can't see any reason why tip up is better than tip down.
Please advise.

Teacher..Ranger wana-be's..

Some of the GI Joe action figures carry knives this way. I'm sure that's a big part of it.

Depends on what you are doing.

On a pack - no. Good way to loose your knife.
On an LBV or a Life preserver it's a different story. You use tip up when you have to engage that tool one handed. Under those circumstances Tip Down is easier to engage with either hand.

I'm sure image comes into it too, but I think part of it is simply the desire to have your fixed blade accessible while wearing a large pack. The inverted carry may be the only way people have seen this achieved and therefore assume it is the best way to accomplish what they are trying to do.

99% of The things you see other people Doing is "Fad". The Survival Thing and Tacticool Thing is in major hype lately. They See People On youtube doing something for out of this world reasons and decide if they do it while doing normal things like hiking/camping, They will be noticed on the trail and identified as something they most likely are not such as "Prepared or Hardcore".

I Dont honestly even see a reason for normal everyday Hiking/camping to have it on your pack straps. I would feel it be more cumbersome then useful. Should I just carry a 12g Shotgun at the ready all the time because SMHTF While Im hiking too? I Personally thing its only smart to do when you Have the immediate possibility of need to cut something off you or cut yourself free from something But not hiking/camping.

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.

Tip up shoulder strap carry makes it faster to get to the knife with either hand. The disadvantages are it's easier to lose the knife and it better be a d**n good sheath or you're going to give yourself a tracheotomy the first time you trip.

In my opinion, the benefits of carrying a fixed-blade knife tip up are rarely worth the risk. It is always a good way to expedite loosing you knife.

In the movie The Green Berets some of the troops carried their knives like that, wrapped in 90 mph tape. I also think in Platoon some of the troops did the same. Tom Berenger carried his push knife like that iirc.

Looks cool. Until you lose your knife. Until the tip up snags every freaking "wait a minute" vine in the jungle. Until you fall on that side and your knife about stabs you in the eye.

Then you put the knife on your belt where it belongs.

Unless you want to be ultra special cool macho and carry a sword on your back... but those people need professional help anyhow.