As that page makes clear, SES can hand off incoming mail to a Lambda, or to S3 – or to SNS which can deliver it to any HTTP endpoint, or e-mail address, or text it to your phone for that matter.
Exactly this. It receives the email, now what? You need to run some code on it and so the way to do that is one of the compute services. AWS isn't forcing you to do anything here.
99.9% of SES users I promise are only sending mail anyway. You aren't forced to have Lambdas or anything else to send mail.
You can absolutely use SES without S3 and Lambda. I've used it many times in various projects.