Shift kits.. do you really need one????

The more I look into a shift kit for a Torqueflite the more I question just what it does and more importantly why they do the mods they do.
I think it's time we really looked at what we are doing to these transmissions and why we are doing it.
Is a shift kit the right way to go? Or should we be actually making some internal mods to the trans to make it shift better?
There are two components, and one piece of information I can see as value in shift kit. Ie, the TF-2
1) The upgraded line pressure spring.
2) The new manual shift valve that charges the converter in Park.
Modifying the holes in the separator plate, if required.
The rest I'm not so sure about so lets discuss them.
First, the orifice restrictor for the 2-3 shift. If the idea is to free up and increase oil flow in the trans, then why would we want to do this? And will doing this shorten the life span of the clutch? Is there a better way??