To answer your question:
Regular steel sizing dies are made of tool steel. When you use them they need a sizing lubricant (RCBS, Hornady, Etc.) or the case will stick in the die which is very difficult to get out.
Carbide sizing dies are tool steel but have a carbide ring in the base of the die that does the sizing. For pistol calibers (straight wall cases) no lube is required. This makes reloading go much faster.
Today carbide dies are the norm for virtually all straight walled pistol calibers.Rifle sizing dies gain nothing with the use of carbide because the cases are not straight walled and the top part of the die does some shaping of the case. To make the entire die out of carbide would be too expensive. Only Dillon makes a rifle carbide sizing die and it still has to use lube.
My first reloading experience was in the early 1960's. The pistol dies were plain steel. I did not reload again until the mid 1980's. In that interval carbide dies had become the norm for all straight wall pistol calibers. Almost without a doubt any non-carbide pistol dies you see for sale today are very old (40 years or more).
In addition the older pistol dies, as I recollect, did not give a tight fit of the bullet to the case (no neck tension). Only the crimp held the bullet in. Today's die sets use neck tension and the crimp to hold the bullet in . This gives a more complete ignition of the powder as the bullet resist initial movement more than in the older designs. That increases the accuracy.
LDBennett