Yes, because e-mails offer the same protection against “reading” as the good old postcard. If you want/need to send really confidential data, such as business data, by e-mail, you cannot avoid encryption. The following options are available to protect messages/documents.
You can of course put the data in a password-protected file and then attach it to the e-mail. The only thing is that it is not very convenient to use and confidential things written in the message can still be read. The password should at least be sent by another means (messenger, telephone, etc.) and not by e-mail.
PGP (Pretty Good Privacy)
PGP uses a so-called public key procedure in which there is a uniquely assigned key pair. PGP is based on the so-called Web of Trust, in which there is no central certification authority, but trust is managed by the users themselves. Setting this up is much more difficult and presents many users with major hurdles.