Normal throat angles are 1 1/2 to 3 today. I don't know what they were 100 years ago - but, corrosive primers, throat errosion from exceptionally hot gasses but to blowby in the throat prior to obturation of a leadcored bullet are what cause throat wear. Soft steels and Damascus steel/iron barrels are also worn noticably by hard bullets, ie: the nickel jackets of years gone buy. This all results in longer throat angles as the rifling origin, the throat is moved down the tube/s, the angle becomming shallower and shallower.
As Bob noted, this also could be a contributor to bore damage.
We haven't addressed rough bores sloughing off soft bullet metal, which builds upon itself making the bore even smaller - many times in a few areas only, at the breech and again at the muzzle where the barrel metal is thinnest.

I'd wager there are a number of shooters who still don't know how to get the copper out, but use something useless for the job, like Hoppe's or Kerosene, then ragoon oil and call it done. The fouling merely builds upon itself every time the gun is fired, the bore becomming tighter and 'stickier' over time.