wuts the deal with the hole?

I kno the theory of digging a decent hole in the ground and mixing in sum essential ferts to enhance the potential of the plant. my question is why is a bigger whole better? i mean trees dont need a big hole to become humungus, or is just so that the soil around the plant for the early part of its life is lose and easier for the roots to spread and move in the soil. im just looking for sum opinions on how much of a difference this makes, wether they be monster plants or decent plants.
thanks

the reason you dig a larger hole then the rootball is it tills up the soil and allows for a much more rapid root growth. it will also receive water down to the roots much better. im sure there is also a couple more reasons.

Simple. the bigger the root space = the bigger the potential. the pot has a limit, but in a hole there's no limit. you ether get the convent pot and a limit, or in a permanent hole with no limit.

yeah, you dig a big hole to break up all the soil or replace it...roots will bury faster, and the plant will grow faster

loose soil helps those roots move