Doing development work, whether it is application development or infrastructure automation, is really hard if you are being interupted frequently.

Traditionally, you avoid interupting programmers by putting some kind of buisness analysis layer ontop of them. That might be a product owner or just telling everyone to communicate requirements through tickets.

But you can't build stuff without talking to eachother. So programmers working on similar stuff tend to chat eachother, sit near eachother. They chat in an informal way.

The trouble is that, for DevOps, often the developers are customers / users. If you chat to them the way you chat to the other DevOps, you'll never get any work done.

Infrastucture automation can happen 2 ways - either the developers take over the IT, or the IT take over that part of the development. IT support organisations have a very anti-customer culture to be honest. Combine that with the need to protect engineers from interuption and you get a very hard silo.