As we have already discussed, having a standardized environment brings with it two benefits. The first is that a well-chosen platform means a long vendor support life cycle. This, in turn, means long support from either the vendor (in the case of a product such as RHEL) or the community (in the case of CentOS). Some operating systems such as Ubuntu Server are available with either community support or a paid contract directly from Canonical.
Supportability doesn't just mean support from the vendor or the Linux community at large, however. Remember that, in an enterprise, your staff is your front line support before anyone external steps in. Now, imagine having a crack team of Linux staff, and presenting them with a server estate comprised of Debian, SuSe, CentOS, Fedora, Ubuntu, and Manjaro. There are similarities between them, but also a huge number of differences. Across them, there are four different package managers for installing and managing software packages, and that's just one example.
Whilst entirely supportable, it does present more of a challenge for your staff and means that, for anyone joining the company, you require both a broad and a deep set of Linux experience—either that or an extensive on-boarding process to get them up to speed.
With a standardized environment, you might end up with more than one operating system, but nonetheless, if you can meet all of your requirements with, say, CentOS 7 and Ubuntu Server 18.04 LTS (and know that you are covered for the next few years because of your choices), then you immediately reduce the workload on your Linux team and enable them to spend more time creatively solving problems (for example, automating solutions with Ansible!) and less time figuring out the nuances between operating systems. As we have also discussed, in the event of an issue, they will be more familiar with each OS and hence need to spend less time debugging, reducing downtime.
This brings us nicely into the subject of ease of use at scale, and we will provide an overview of this in the next section.