So I've been thinking more about this as to why?

It is quite obvious that it is driven by Redhat to be the same as Oracle
Solaris, they say as much.

The base reason I can see is part of a marketing job showing the
apparent ease of change when trying to sell Redhat servers to replace
Oracle Servers.

It is better to force Linux users to change if you can show potential
high dollar clients that they don't have to.

The support of the systemd folks and cronies is merely leverage across
the distros.

The Corporate vision is once again driving change for their benefit.

To my simple mind the logic of the change seems backwards, I find it
easier to see a case for sym linking from /usr to / than the other way
round.

Clarke "the guy in the tin foil fedora"