I’ve worked as an IT architect at various companies in my career and you can definitely get support contracts for engineering support of RHEL, Ubuntu, SUSE, etc. That isn’t the issue. The issue is that there are a lot of system administrators with “15 years experience in Linux” that have no real experience in Linux. They have experience googling for guides and tutorials while having cobbled together documents of doing various things without understanding what they are really doing.
I can’t tell you how many times I’ve seen an enterprise patch their Linux solutions (if they patched them at all with some ridiculous rubberstamped PO&AM) manually without deploying a repo and updating the repo treating it as you would a WSUS. Hell, I’m pleasantly surprised if I see them joined to a Windows domain (a few times) or an LDAP (once but they didn’t have a trust with the Domain Forest or use sudoer rules…sigh).