It offers significantly more flexibility and freedom compared to any social network. If your data is "hijacked" (not sure that that means in this context, but let's assume the host terminated your account), you can spin up another hosting account on one of the many hosting providers and point your domain to it. That's it (not to say that it's that trivial for large sites, but that's the gist of it).

If your account on a major social network is terminated, if you had a large community there, you have quite literally no way to access them unless you had some kind of parallel presence somewhere else.