And when they do have to travel in a way that would impact their performance, it's major news (in the baseball world) for days. I remember when the Detroit Tigers had 4 games within 48 hours in different timezones [1] and the MLB got some serious criticism for it. The Tigers had to pull some of their best (and highest paid) players due to lack of sleep.
Twice last season, the Giants had to play in Denver (5200 feet altitude) traveling from other cities with no off day. One of these was a day game immediately following a night game in Chicago.
[1] https://www.freep.com/story/sports/mlb/tigers/2017/05/26/det...