Don't know, but limiting game new releases to outdated sytems certainly is.
This is the silliest take.
Psst. This may shock you. The PS2 got games until a week before the PS4 came out. Turns out many people don't really mind if a system is """outdated""", what matters is game quality.
And a Etrian Odyssey just needs a (3)DS to work properly. Just how it is. This game can't be ported without losing most of its appeal.
Any version of the series for the switch will have to be very different, and thus may appeal to different people. It'd be silly not to bring it over, the audience exists.