It's simple to add and manage.
You can integrate with MailChimp.
User tracking is brilliant.
Can show on exit intent.
Best, it's effective.
Can't implement it for a variety of cases.
No step of the 3 can be skipped.
It's great if you want Email subscribers. It works well with its default format.
But you can't alter it to use in any other case, like to show a banner with button linked to another page.