Really good question. So many of the templates do not require you to be subscribed to a mailing list. A good portion are designed by the ONTRAPORT design team or ONTRAPORT and ONTRApages users. All of those ones are either free or paid and do not require an opt-in. The ones you're seeing that do require you to opt-in like this one
are posted by ONTRAPORT Certified Consultants. One of the options the ONTRAPORT Marketplace gives them is to share their templates in exchange for email addresses so that the consultants can connect with ONTRAPORT and ONTRApages users easier.
I hope that helps! If you don't want to share your email address, I would suggest choosing some of the free templates instead.
Finally, thank you so much for the kind words about the product looking exciting! We're very excited about these new features!