Some software vendors - e.g. major engineering applications - only support their products on RHEL.
If you open a support ticket and say "Hi I'm using Debian/Arch/Nix" they will just laugh and close the ticket.
SAP: https://community.sap.com/topics/linux/supported-platforms
PeopleSoft/Oracle RDBMS: https://docs.oracle.com/en/database/oracle/oracle-database/1...
But yielding that point would mean that RH/IBM would have you over a barrel on pricing. Probably why Suse is forcing the issue.
P.S. and Oracle is piling on ...