As far as email is concerned, one reason why you don't see as much as self-hosting or any frankly, is due to deliverability. Doesn't help to have your own mail server when all the mail coming from it is classified as spam and filtered out of inboxes leaving you to have to use a "trusted" hosted provider to ensure your email actually works as you'd expect.
Is it really a problem or cargo culting? I certainly thought it was a problem, but I know a sysadmin that runs two small businesses's email on prem and he says that deliverability, even to major providers, has never been a problem, as long as you set up everything right.
I don't know how cargo culting figures into this. Nobody is setting up cardboard boxes and thinking it's a mail server :).
What does it mean to set everything up right? Out of the box postfix, sendmail, dovecat, etc., no longer generally work, even with DKIMs, and other necessary domain verifications.
I have heard of some admins opening cases with some of the large hosts to ensure their mail goes through, but seeing how those are all big cos with little no guaranteed lines of contact or follow through I wouldn't hold my breath on it working or being a long-term solution as they can easily blacklist you at any time with you having no recourse.
I'd love to hear a counter argument, as it's also the same thing for basic transactional mail sending, there's a reason everyone switched to SMTP hosts such as Mandrill, Sendgrid, and AWS, deliverability.
