I have reason: Costs. Recently in my region, Spotify racked their price from ₱129 to ₱149, ₱10 difference with YouTube Premium.
Plus, Spotify keeps shoving their podcast platform on my feed, which is annoying, and I’m only streaming music. I rather see or listen to something from my followed channels.
P.S. I only created a Google account just for YouTube and for my Android device, nothing else. I don’t use other mainstream Google products.