Why do the .deb and .rpm packages leave the service offline?

I’m super excited about the Debian package being available. It makes managing all of the nodes in our clusters much easier.
I noticed that the preinst script stops the running service. I don’t really understand this choice, but it doesn’t bother me nearly as much as the fact that the postinst script doesn’t restart the service.
My company diligently updates our servers to the latest packages, so if we’re not careful, and I hadn’t noticed this fact, the next release of Opensearch and Opensearch Dashboards would leave us completely down.

What is the reason for this behavior?