They're still quite popular in Europe and especially in Germany whereas Redhat has utterly dominated North America.
Anecdotally, i feel like RHEL dominates the UK enterprise linux market as well as NA
nods head Yup, sounds about right.
SUSE is used pretty widely used in the European financial sector, right? That’s what I remember hearing the most about it.
EDIT: I’m referring to non-personal workloads, i.e. enterprise. Pretty much everything I’ve come across in a working environment has been Red Hat based, I’m not talking about personal local or VPS environments. Ubuntu and Debian do have a presence, but not at the Red Hat scale from my experience.
Scientific Linux, which was built exclusively for HPC, was based on CentOS.
SUSE may be overlooked from a US perspective, which is why they get much less coverage than they deserve on sites like HN. They are huge in Europe and employ some exceptionally good people, and have been making probably the most solid distro out there since ~1994.
The market is big enough for multiple large Linux distributions (Redhat, SUSE, and Debian^WUbuntu*). The market continues to grow as more things transition to computers.
SLES is recommended for SAP installs, a huge enterprise market.
https://wiki.scn.sap.com/wiki/display/ATopics/Supported+Plat...