The same kinds of psycho who promote Secure Boot. They _really_ believe in a security strategy which _requires_ everything that could be potentially be compromised to not be signed by Secure Boot. The moment you have something signed which has a vulnerability, you can use it to decrypt everyone's SecureBoot+TPM encrypted hard drives.
Why that ever was considered a valid security approach is over me, as there is an entire gallery of vulnerabilities like this one. It also completely ignores the elephant in the room called Windows.
Example of this type of thinking: https://lkml.org/lkml/2018/4/3/767
Note that despite Linus' reticences, in a lot of distros integrity mode is indeed enabled when you boot with Secure Boot on. Likely because of MS politics and distros wanting an MS UEFI signature being forced to "go through the hoops" as explained in that thread. As a result enabling Secure Boot usually cripples your distro, preventing you from e.g. hibernating.