Meta Ads are rented reach. You pay to put a product in front of people who match a profile, on apps they already scroll. Nothing else a small shop can buy reaches new people as quickly.
Email is owned reach. Everyone on the list already knows you, and sending to them costs the same whether you email them once or fifty times. Nothing else a small shop can run is as cheap per sale. The case for email on its own is in email versus social media.