To the best of my knowledge, Automattic followed the success of the Wordpress open source project. It's an attempt to monetize an existing open source platform. The same goes for Docker, Elastic and others. The open source platform came first, then came the services.

Broadly speaking, I don't know why software is singled out in its economics. Creating software takes time of people. Time costs money, and much more of that when it comes to highly skilled engineers. The fact software has virtually no replication costs does not change the fact that its engineering is as expensive if not more so than engineering of other goods.