Earlier quoted context omitted.
It's not just taking advantage of forgetfulness, I think there are a number of additional psychological factors that make you more likely to keep it active. Off the top of my head, I'd say: laziness might make you convince yourself that it's not a big amount, there might be a sunken cost fallacy at play (similar to how phone agents keep you on the line on purpose, which also serves to make you feel like you didn't wa…
And the unsubscribe process might be a chore: at least that's what happens with email subscriptions.
I have had to write an angry email to a paper because they though they could get away with only doing phone unsubcribing (when they did signups just fine online).