As noted above,, with carbide dies,, it may not be NECESSARY.
However,, as a trained machinist,, I can attest to a few facts. (Although I no longer work as one.)
Just because you can,,, doesn't mean you have to,, with many things.
In handloading,, clean dies will last longer. I have seen damaged carbide dies from not cleaning them occasionally, or using dirty brass.
Lubing brass. As noted,, carbide dies can & are used w/o lube. But as a machinist,, when two dissimilar metals meet,, having a LIGHT lube is always a good idea. It reduces the friction. It allows the tools to work better. It helps protect the tools, and the work piece.
And stresses upon metal causes a thing called "work hardening."
And yes,, I have had people bring me carbide dies,, with stuck cases inside,, rims ripped off,, to help them fix things.
Lubing years ago meant putting a gooey heavy feeling oil on a pad, hand rolling the brass to coat it. It was time consuming & a bit messy. Still is,, if you go that route,, as compared to modern pump or spray lubes that are designed for handloading.
I always tell new reloaders a few things;
If you want to make quality ammo,, look at the paid professional competition shooters & what they do. Those that reload,, use certain things, do certain procedures, and make their ammo the best they can. Their JOB & all DEPENDS upon them performing well. Ammo issues can kill them. Rarely do any of them have such problems,, in a match,, because they have worked out all the other issues beforehand.
So, study their equipment choices,, study their methods of ammo assembly, and you will see a pattern emerge if you ask several of them. (This eliminates the sponsors choices used by a few.)
A good example is how the USPSA does a survey of the stuff used in the Nationals by ALL competitors, (or at least the ones who fill out the surveys,) and publishes the results. It's interesting to read the results. In fact,, they used to do the surveys years ago,, and just recently went back to doing them after several years of not doing them.
Some equipment,, changes due to design improvements. But when it comes to reloading,,,, much of what was good in the 90's & early 2000's,, is STILL used today.
Now,, I know people who never clean their guns. I know some who load whatever brass they have,, including steel Wolf stuff. I've even seen one guy who re-used split brass by putting fingernail polish over the split.
My point?
A lot will work. But do you want to make truly good ammo & have your expensive equipment last, or not?
Lubing brass doesn't hurt anything,, even when using carbide dies.