It's SE's vow to consistency. Same pattern for each patch regarding horizontal and vertical progression.

Because it's patches that dictate when content is released...expansions are honestly just a big terrain patch which opens the world and the possibility of new content for FFXIV. From 3.0 to 3.1 which, on SE's time line is a proposed half a year, you get a Alexander release, normal and hard, void ark, and max level 4-mans, all of which stay prevalent till 3.2 where the new Alexander tier is released.

So now in re-evaluation, you have horizontal progression with 4-mans, primals, void ark, and Alexander normal as horizontal progression for each patch whereas vertical progression is prolonged inbetween every other patch.

With this mindset, obviously SE wants everyone to try the vertical progression.

This is like SE's the parents with a huge mansion (savage content) and we are their children, sadly only 1% of the children come to visit the mansion and stay for a while lmao