2 reasons: I have a 'personal' Substance account and Creative Cloud work account...I can't work with decals in Stager as "photoshop' is not signed on ...2) I don't want to locked into Creative Cloud licensing.
Right now the edit action is automatic based on format (raster images to Photoshop, vector to Illustrator). I'll check with the team if it's possible to customize this or provide a drop-down for options on what app to send it to. I'm curious what app you want to use? We may be able to pull a list from the OS, or just go with "OS default" as an option or something, we'd have to look into it. I'll move this post to the 'ideas' category!