Need to resize the cases systematically ...?

[BruniX]

We sometimes hear that resizing cases is only useful if you want to shoot the cartridges in a rifle A,
reload, then shoot them in a rifle B.
Indeed, the case will be dilated in the room of the carbine A to marry perfectly its dimension.

It could therefore be reused directly in the SAME rifle.

What should we think of that

[Steve51]

I resize the case every time I reload the case. My press de-primes and resizes in one step. I also resize new bought brass before loading - may not be necessary but that is what I do.

[JEBar]

I resize our brass every time .... years ago I tried skipping resizing because the shells were used in the same rifle .... it worked but the action didn't seem to operate as smooth .... resizing shrinks the diameter by a tiny bit .... I believe that returning the case to its "like new" shape made a difference

[BruniX]

ok !
we rarely have time to do well, but we always find time to redo

it's better to do things well ...first time...

[Ojaileveraction]

We sometimes hear that resizing cases is only useful if you want to shoot the cartridges in a rifle A,
reload, then shoot them in a rifle B.
Indeed, the case will be dilated in the room of the carbine A to marry perfectly its dimension.

It could therefore be reused directly in the SAME rifle.

What should we think of that

Speaking directly to your question.
If you are seeking to tease out every bit of accuracy a shooter may only "Neck Size" the fired case from rifle A to use in rifle A. If you didn't resize the neck, the tension would not hold the bullet.
Really used for competition shooting, not for reloading Hunting Bullets.

[mrguvna]

for safety sake I always full length resize all cartridges. If they are going to be hunting rounds I will also trim after sizing so as to make the crimping more consistent. I tried neck sizing years ago for my 30-30 but was not pleased with the outcome and took me off my routine I get into prepping cases. I like to stick with a consistent process in prepping brass, inspecting throughout the process for any problems.

[Mistered]

If you are seeking to tease out every bit of accuracy a shooter may only "Neck Size" the fired case from rifle A to use in rifle A.

This is correct.
Neck sizing only is a specialized process typically for long range breech rest shooting where the goal is the utmost accuracy. Along with neck sizing is 'neck turning' where the case necks are 'turned' (as in being cut concentric) with the neck wall equal thickness.
This is all good and fine for those who are looking to shave 'thousands' off of groups but the average shooter can achieve excellent accuracy from reloaded ammo by just taking care to ensure they are consistent during their reloading processes and carefully working up loads and testing for optimal accuracy.
One final word on resizing though - straight wall cases need to be full length resized regardless of how or what they are loaded for to obtain optimal performance in lever action rifles.