No one owns their social media accounts, social media not only controls who sees our posts and when they see them, they also have a right to inactivate or delete your account at any time for any reason.
Email, by contrast, is an asset you own. Although it is hugely frowned upon selling or renting your list, it still adds significant value to your business. You can take your list with you and use it on your choice of platforms to send out messages. Would you rather have a business with 10K social media followers or 10K engaged email contacts?