Opening Day - This is a different discussion. Having a day opener is a good tradition, especially in a good baseball town. But, other than in Cincinnati, the first month should be heavily front loaded to domes and warm weather cities.
Regular weekday day games - I have never understood this. The traditional practice is to play M-T-W or T-W-Th with the last day being a day game (of course, Su as a day game in a weekend series goes without saying). This is a remnant from 60 years ago, when the world traveled by train. Teams played a quick day game and headed to the station for an overnight to the next city. (Another remnant of the past is the union requirement for a post-game buffet, left over from when it was hard to find a table after 9PM, even in a big city). With teams flying charter, this makes no sense at all. Contrast to the NBA or NHL, where late night travel is common. In most markets (there are exceptions) these weekday day games are throw-aways. Not televised or with micro ratings if they are. Small live gates. It is just tossing away 8 or so events. Not good business.
My "warm weather" theory. Ever notice this? Lots of people live their lives in warm weather. Most Latin American players, many North Americans from places like Florida, south Texas or SoCal, etc grow up in places where it is never really "cold". And lots of players go home as soon as the season is over. Thus, maybe 10 or 12 days in April and the post-season are the only times they are outdoors in the cold in their lives. Contrasted with people from most of the USA, Canada or Japan, who participate in sports, including schoolastic baseball, in very poor conditions. And warm weather players, both pitchers and hitters, are notoriously slow starters when they are with cold-weather teams. Same theory, BTW, applies to golf. Guys that grew up playing in all conditons are much better at playing in poor conditions than guys who grew up in the deep south or SW.