I do. It helps to have it all in one place. Also since I'm paying for Spotify, I'm glad I'm not paying for another separate podcast service, and it feels like I get my money's worth. Probably listen to a good 3-4 hours of podcasts per week and another 20-30 hours of music. If I was JUST doing podcasts, I'd probably use another service but it's nice to have it all in one place that behaves the same for me in the car.
I see what you're saying. If for some reason podcasts became untenable on Spotify or inconvenient for me I would probably look more into a service like that. As it is though, my 2-3 hours per week are fine on Spotify. Good to know there are other options out there though.