The main problem is Spotify isn't a podcast app. I don't listen to music like I do podcast, and I don't want my queue there because music would mix in, and it can easily reset.
Also, most "real" podcast app have better playback options. I want to be able to see chapters, and skip silence, but forcing to use Spotify for an open format is bad for everyone. Podcasts are great because they are open, and give you choices in playback apps.