This is an introduction of a vulnerability.
Servers can avoid reboots for long periods of time, but not forever.
Once you need serious uptime, you will have more than one server providing the same services in either a failover / load balancing type arrangement, and individual servers can be rebooted without creating a service interruption.
Much too risky to allow realtime kernel patches for sake of convenience of no reboot, IMHO.
Great! Modern operating systems get something Vax/VMS had 35 years ago. Progress!
It seems that more and more applications and software packages have memory leaks that tend to hold on to chunks of memory, and normally about the only solution is a reboot.
That is really cool.
I have to admit, I am a tad disapointed. I was hoping that by Linux 4, we would have migrated to the Minix3 kernel, and by 4.2 would be adopting isolated device drivers.
sigh
But patch on the fly is good. Will have to revisit the RHEL certification.