From top of my head:
- Redhat and Suse have LONG binary compatibility, like 20 years. Debian has 3 or 5 years?
- If something goes wrong, you can sue and get something. Debian has no money.
- Redhat and Suse actually develops linux kernel, underlying filesystems etc... Very important if you have weird concurrent database issue on large cluster.
- Debian is political and has no commercial predictability. For example there is very small chance it may decide to abandon systemd and move to something else.
- Commercial certification; you wont get SAP R/3 or Oracle support contract for Debian, even if would manage to install it.