Game has changed over the years
1901-1919: The Dead Ball Era
Oddly enough, this remains the only era that has a widely accepted label.
And a well-deserved label it is, as the baseballs of the era were indeed dead. At that point in the game's history, both leagues were still essentially experimenting with the baseballs, and the baseballs in use for most of this era simply weren't designed to be hit particularly hard or far. What's more, beginning in about 1905 pitchers began doing all sorts of disgusting things to the balls: They spit on them, they rubbed slippery substances on them, they scuffed them with sandpaper, they gored them with the spikes on their shoes. Basically, if you could think of it, pitchers in this era were doing it.
What's more and more important, probably most players of the era simply weren't trying to hit the ball particularly hard or far. This led to low batting averages and very little power-hitting; in 1908 the American and National Leagues combined for a .305 average that is, a .305 slugging average.