by the logic I keep hearing if I declair "I climb the tree to find the cow" there is no way to separate the climb that is uncertain from the find the cow that is certain (not up there) it is all or nothing
It becomes an important distinction in connection with social interactions and roleplay. Contrast -
DM: Here is a tree.
PC: I want to climb the tree.
DM: You are tied up, so you cannot climb the tree.
PC: I want to wriggle free of my bonds.
DM: Here is a tree.
PC: I want to climb the tree.
DM: No, you do not want to climb the tree.
PC: ...
What can the PC attempt in the second case? What is their approach? We could consider -
PC: I focus my will on wanting to climb the tree.
DM: I'll call that a contest of your CHA versus CHA of NPC who persuaded you to not want to climb the tree. You can both add Persuasion.
I think there are a couple of reasons not to go that route. One is that we've never had good rules for social interaction. Compare it with Athletics which is used in several detailed mechanics. Grappling for example, which falls in the scope of ability checks (unlike Attacks.) Or jumping. So ones first objection might be that the rules are not robust enough to support it well.
Why are they not robust enough? If we want to know a reasonable distance to jump, we have measurable real-world examples to help us. But what is a measure for battles of will? In our world, the psychological or cognitive is much less well understood than the physical. It's hard to find a normal that everyone can agree on, and for many players it's just not that much fun to be told what they
want to do! Given that's pretty much their only power in the game. (It's in fact a
tremendous power, but obviously much less tremendous if you can easily take it away.)
For me that is a useful insight one can take from the OP. If your only power is choice over what you can do, then you reasonably enough feel strongly about protecting it.