The owners did away with Double Headers, which use to be fairly common, now they start earlier in the year in order to avoid double headers and sell every ticket to every game at premium prices.
Years ago, even the MLB all-star game was a double header.
Also there’s an extra round of playoffs at the end of the season.
Back when the MLB had 24 (or 26?) teams they did try starting the season in warm weather sites one year.
The schedule did work out nicer though if they did one circuit of the division, one circuit of the opposite division, one circuit of the division, one circuit of the opposite division, and close out the season with one circuit of the division.
When the AL went to 14 teams one team had to play the opposite division during each mini-circuit.