What people want are systems that compose and work well together. That's what MS provides, or at least attempts to provide, with SharePoint. When you start tryi

What people want are systems that compose and work well together. That's what MS provides, or at least attempts to provide, with SharePoint. When you start trying to tack on collaborative document editors, workflow management systems, shared storage, and other capabilities from different providers or systems you run into more and more complications (especially because most of these don't offer any kind of standards compliance that lets them be used interchangeably). That's also why G-Suite works as a competitor to MS, it covers at least the more critical integrations that people want to work smoothly without needing to combine multiple maybe compatible things together.