That's kind of survivors bias. You are not aware to the mass of mail that doesn't appear in your mailbox. When you are in the sending side, you quickly find that you don't reach your audience.

If it was open you would probably be receiving hundreds of them a minute. The filters means many don't even try, but if the required effort was zero we would be flooded with them.

The situation was so bad before the filtering products were invented that Bill Gates tried to push small fees (stamps) as a requirement for sending emails (https://www.cbsnews.com/news/fee-based-e-mail-way-to-can-spa...).