Honestly, no, you don't need a team. It is good practice, but not necessary. I've worked at several companies where the production build was made from a tower under a desk or a server blade, or an iMac on a shelf, sometimes one guy knew how it worked, sometimes nobody did, sometimes the whole team did. In most cases, managed by the product's dev team. IT just firewall-wrapped the crap out of them.
Not to discredit the main meta thread of "we don't have to manage anything with cloud" vs "having management team" debate. Odd thing is, cloud prices are climbing so rapidly that the industry could shift back in a near future.
Bottom line for most business though: As long as the cost makes sense, why bother self-hosting anything. That's really what it comes down to. A bonus too, as most companies like being able to blame other companies for their problems. Microsoft knows that, and profited greatly with Windows Server/Office/etc. for that very reason.
When your quarterly profits are dashed because an employee backed into your server room and turned on the halon fire suppression system and you gotta rebuild from scratch from month-old off-site tape backups, how do you write a puff piece to explain that away without self-blame or firing the very people that know how it all works?
When your quarterly profits are dashed because Microsoft's source control system screwed up, you make a polite public "our upstream software partners had a technical error, we've addressed and renegotiated," message, shareholders are happy, and customers are still stuck with a broken product, but the shareholders are happy.
My general contribution to the conversation is GitHub should have a donation system. Once a week, some kind of donation raffle happens, and the winner gets GitHub taken down for "reasons" for 4 hours, then 5, 6, 8. Microsoft profits more, and it slowly becomes a technology-and-money-induced vacation day.