I'm not picking on you or anyone else who chooses to tote a knife in a tree, but I have never understood the reasoning. On the outset, it sounds like a good idea so someone can cut your rope free in an emergency. But.........
When was the last time you or anyone else cut a lifeline in a tree? Standard Operating Procedure for aerial rescue as I was taught by Davey Tree was to lower the injured person on THEIR OWN LIFELINE AND HITCH. I was screamed at because I untied the injured person's hitch AFTER securing his lifeline so I could lower him. I probably would have been fired if I had pulled a knife out!
Under no curcumstances would I want someone coming up into a tree to rescue me with a knife. If they do not understand my friction hitch or life support system enough to lower me safely, I certainly don't want them cutting my ropes! In all my years of climbing I have never come across a need for a knife in a tree. I have one in the truck but I am not going to tote it up a tree with me just to look 'safe'.
You can come up with a bunch of "What If's", but we can do that untill we determine it is unsafe to get out of bed in the morning.