I'm a developer whose transitioning into Devops. By observation, I've noticed that a lot of dev shops have started using Octopus Deploy and Azure Devops Services (AzDo, formerly VSTS), or they are starting new projects to setup devops ci/cd pipelines AND they spec to use both tools.
I've been through some quick training for both tools and though they aren't perfectly the same, AzDo seems to offer all of the same features as Octopus Deploy.
So, my question is if a company is already using AzDo for much of their version control, or anything CI/CD pipeline-related, why would you use Octopus? What benefit does it offer to use Octopus for your build and deploys to AzDo?
Note, I am very, very new to Devops. I'm just asking because at the "10,000 feet view" there doesn't seem to be any reason for Octopus if you're already using AzDo. I mention Octopus Deploy by name because I see it come up frequently. However, I assume there could be other tools that serve the same purpose of automatic build and deploying that might also integrate with AzDo. However, AzDo offers build and deploy built in one. Why split out the work?