The strike zone is getting really, really big
In the 90s there was a lot of talk about the strike zone expanding to the right and left, especially for pitchers like Tom Glavine and Greg Maddux who could consistently hit points outside of the zone and convince umpires to give them those calls as a result of that consistency.
But overall, the zone was a lot smaller then. The offensive numbers certainly bear that out as both the high strike and the low strike all but disappeared and hitters could crush anyone who couldn’t paint those corners (or just outside those corners) like Glavine and Maddux.
The wide zone doesn’t exist now like it used to. Most attribute that to Pitchf/x, which Major League Baseball has used to grade umpires over the years. They’ve been called out on that leniency and have called a more accurate zone, laterally speaking.
But boy howdy, it has grown vertically. As Jon Roegele demonstrates at The Hardball Times, the zone has grown and grown significantly, and it more than anything else is what has led to the low offensive environment and lack of contact we see in today’s game:
This is the sort of thing that leads to the league, however silently, making adjustments. Formally redefining the zone or leaning on umpires to informally change things. Possibly, as definitely happened in the National League in the 1930s and many people suspect happened in 1987 and 1993, juicing the baseball.