Redhat Enterprise. Designed for running commercial software. Response to criticism about unstable and rapidly changing early Linux distributions. Snapshot of Fedora Linux. Tools for a major release of RHEL are never upgraded. They only receive fixes to improve reliability and maintain binary compatibility for closed-source applications. Libraries and tools much older than bleeding-edge Linux distributions that are more popular among individual users. Trade modernity for stability and compatibility.

Most HPC clusters run RHEL derivatives.

Ubuntu, which is based on Debian, is popular among individual users due to its ease of installation and management via graphical tools. GhostBSD provides a similar experience on a FreeBSD platform. The Debian family also has the largest collection of quality-controlled packages, with FreeBSD ports not too far behind, and with a higher percentage of packages running the latest release. (repology)

Unfortunately, many scientists still perform caveman installs of scientific software on Linux systems rather than use a package manager.