TBH for me it is the principle than the time savings.
If I have to call and cancel, that is basically a guarantee I will never use you again and will warn everyone to not use you.
If I have to jump through a bunch of screens, I will be mildly upset but will probably forget about it.
I just don't want to support that behavior, so these companies basically being forced to do so on "my" (really apple's but I am making a choice to use them) terms is worth some financial cost to me.
If I had thousands of subscriptions, maybe I would be saying something different. But the yearly additional cost in this theoretical situation is minimal and to me it sends a signal. If I actually was given that choice then the company can see those metrics and hopefully see why.