I spend a lot of time making a rifle. I would like it to last as long as possible......long beyond what is left of my lifetime. I use Acraglass to do repairs, but more than that, I bed the last 6 inches or so of every barrel and the barrel tang area on every rifle .....for two reasons. First, I am not bad at doing a good inletting job, but no matter how long I spend at it, I cannot get 100% contact between the metal and the wood. Some part of the breech and / or tang will be in contact with wood while other areas will not be. Since I slot the barrel lugs, the keys or stock pins do nothing to resist recoil. The only thing that resists the rearward force of recoil as the weapon is fired is whatever metal to wood point of contact there may be in the breech area or along the tang screw. Now my inlet job on a .54 caliber rifle may last a 100 years, but when I bed the breech and barrel tang area, I know I have a nearly perfect 100% contact between the barrel and stock to spread out the recoil load. It is the best way I know to insure the highest strength and longest life in the weakest area of a stock.
Second, the vertical face of the breech inlet is all end grain wood. Hard to really seal well with most finishes. When that area gets wet (walk in the rain, leakage from the touch hole during cleaning if you don't always pull the barrel out of the stock for cleaning), the wood in that area can absorb moisture, powder residue, cleaning fluid, ......whatever. When I bed the breech area with Acraglass, it is substantially and permanently waterproof. No end grain absorption possible.
So....since I would like any gun I build to last as long as possible, and since you can't see the bedding when the gun is assembled, I think it does some good (better recoil and water resistance) and certainly no harm to bed the breech area. As JerryWH says......"The gun makers in 1790 used the best things and materials at their disposal and I do the same thing."