ELI5: How is alias email forwarding a good thing for privacy?

I'm having trouble understanding the benefits of this concept. Let me explain, I'm talking about the services that let you create alias emails such as annonaddy, mysudo, altmails, ddg, there are so many companies now. Yes they let you create an alias to share with the end company, but instead of the company your emails are stored in that service provider's servers and sold to the highest bidder. They know what all your aliases are, and they can keep those …

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