why all zones should be practiced.

[wenshu]

So... eat bitter.

Eating bitter goes without saying at this point. To be precise; eat bitter where you are weakest. If you are already eating sh*t, eat worse sh*t.

Unless one's strength is eating sh*t. Then time is better served adapting to putting a warm, moist dent in a musty Laz-E-Boy emptying the contents of a pallet of Hot Pockets.

There is a trick though:
First we must identify our strenghts and weaknesses and then overcome our weaknesses VIA our strenghts.
EX:
If your strength is striking ( and that means one of 2 things:
You have KO power and/or you strike better than you do anything else) then you must overcome your weakness ( ex: ground work) by adapting your strenghts to WORK in THAT area.
You don't become a grappler, you become a striker that can strike withing the grappling context: Clinch hitting, "dirty boxing", GnP.

You're talking about in situ combat tactics.

I am talking more about after you eat some knees in the clinch, you go to the gym and eat more knees in the clinch on purpose, work neck bridges, posture, escapes etc until you adapt and become at the very least nominally capable in the clinch.

Then, when competing, sparring, fighting off baseheads, whatever, you can work it into your tactics.