> I do this because it allows me to directly reach out to users, provide them with on-boarding emails/updates, and build a mailing list of people interested in keystroke automation (my domain of software).
What if I don't want to be contacted? Am I expected to provide an email address, wait for the first marketing email (which I never asked for, BTW), and then unsubscribe?
> the richness of interaction you can have with customers over email
There's certainly some survivorship bias here. [2] You also need to consider all of the prospective customers that are turned away by this requirement. (Those who elect to sign up for the free trial are, by definition, willing to provide an email address and probably more likely to interact with the developer.)
Perhaps you should run an A/B test to investigate the effects of your email requirement. The data will speak for itself!