You might be an exception. If you leave a service, you probably will never return. It might still be more profitable to just make sure the customer stay as long as possible by creating barriers to leaving.
I've gone out of my way to cancel (and permanently ignore) certain services in the past when I discovered how difficult it was to cancel (and port my data).
I've lived one place and needed an internet connection, moved in with someone so I didn't need an internet connection, moved again and I needed a connection again.
I've used Trello, closed my account in preference for Jira, then later in a different job with different needs used Trello again.
Hell, for a lot of products I'd say that former customers - who have a proven need for the thing the product does, and a proven willingness to pay for a product that does it - are probably the single demographic most likely to be future customers.
And our remembrance of a thing is heavily weighted by the last or most recent part of the experience.
Businesses will go to any lengths to get a good review on Yelp or whatever, but are happy to permanently contaminate the experiences of every single one of their experienced customers by making it really hard and painful to leave. This is crazy.