I don't have any insider knowledge, but it's not hard to imagine a customer with a fleet of machines that will run out of LTS soon. The project that replaces them is already on its way, but of course delayed.

So now, what do they do? Spend thousands of hours upgrading the soon-to-be-replaced fleet anyway, or ask their vendor if they could, pretty please, extend LTS for another two years?

If Ubuntu can spread the cost between enough (or large enough) customers, why not?

I know that there is still rhel6 customers in contract, that was 2010.

The "Extended Life Cycle Support Long-Life Add-On" could carry RHEL6 until 12/2027, according to https://access.redhat.com/support/policy/updates/errata.