Content isn’t “free” if it requires an email.

The email is the currency.

Gating content doesn't use an important principle:

Reciprocity.

When someone has paid for your content…

You haven’t really done them a favor.

They’ve paid for it.

They’ve given you something of value.

You've done the same.

That’s a transaction.

When you GIVE something away though…

That’s a gift.

And receiving gifts evokes a sense of reciprocity.

Which is a good principle to use in marketing.