That has two problems. 1) If your machine doesn't have an option to turn secure boot off you are knackered and 2) If you _want_ to be able to secure yourself against malware booting the wrong thing (which is a reasonable thing to want), just turning the feature off isn't ideal.
1) Will happen if your server is ARM-based and the vendor of the hardware wants to make it possible to run Windows. They are not _allowed_ to put the 'disable' feature in the BIOS if they want a 'certified for Windows' sticker. Are vendors going to supply two versions of the hardware - one certified, one not? (Maybe two BIOSes would suffice and you could choose to install the 'generally useful but not certified for Windows' version - so long as one is supplied).
2) Restricted boot is actually useful so long as you have control over which signing keys are accepted. They you can sign your kernels and protect against a set of attacks. It's the control of keys which is the important bit. For things like remote servers I can see this being quite a useful feature for some people, like selinux is.
I really don't know what's going to happen with that ARM restriction. It's not going to be popular with a good chunk of purchasers, especially of server-grade stuff. And it'll be a massive pain on mobile stuff too, although to be fair if you bought mobile hardware running Windows-anything over the last decade you were usually screwed when it cam to putting your own OS on there (for boring difficulty-of-reverse-engineering reasons), so maybe things won't change that much and it'll remain unpopular. The important bit is still 'who controls the keys in the bootloader'.