A short list:
Long commercial breaks.
Too many players on a team, especially pitchers.
Too many pitching changes.
Small playing fields.
Loud music (sic) and exploding scoreboards.
Too many young kids in the stands.
Roaming concessionaires clogging aisles and blocking views.
Interviews with players (especially hairy ones).
Interviews with managers and coaches.
More than one announcer in the booth.
Small strike zones.