The reason for the others changes is so that they conform to the actual season.
For example, the July setting will be for the end of the regular season and the very first game of the playoffs. You will have to set your August prices without knowing for sure whether you will be promoted or not.
With a 14-week season, and 13-weeks per 3 calendar months, they will slow drift, so that using calendar months, you will be setting prices at different times during the season. The start of the season and the ASG would be convenient times to set a new ticket price.