Because the purpose is to read disks protected by technological protection measures. Circumventing technological protection measures is illegal, period. That's one of the things many people don't like about the DMCA. I'd recommend to start archiving this website now.
I mean, the post is from 2019, and MakeMKV has been around much longer than that. I know this isn't always the case, but I feel like if they were going to take down MakeMKV's site, they probably would have done it by now.