Post 70% overlap statistic, publishers have to consider whether the addition of a Switch version at launch would boost sales enough to make that version worthwhile or just cannibalize sales of other platform versions. Late releases allow the publisher to market the title as a more unique experience despite content parity and completely avoid the possibility of taking away market share from PS4/XBO. There are drawbacks as well though. No marketing push and cheaper versions are an issue, but I guess that's when you're hoping for a bit of the Switch magic to help you out.
If the majority of the market your game targets is already likely to have an accessible platform to play it, adding another does little to help you. I'm one of those weirdos that really like playing games on the Switch though.