Because imo... that is the answer. We have seen so many stupid closed ecosystems of home automation stuff come and go, I dunno why you'd mess with anything else at this point. In fact I just got another email reminder that Google is turning off the old Works with Nest stack. Remember Nest? Yeah...
I totally get how that's off-putting, but the real recommended way to run home assistant is to install Home Assistant OS on dedicated hardware. Which also can be off-putting.
Either way, it's my favourite software that I regularly interact with (unless you count Linux).
The "Supervised" installation (i.e. installing Home Assistant on top of an existing Linux install) is doable, but not preferred.