You can’t move your X or FB account. They can block you anytime, or reduce traffic. Way fewer options.
Just owning your own domain, minding your own business, doesn't guarantee that it won't be taken down on a whim.
“But also, as someone who relies on your site, thank you so much for handling this in such a quick and effective way. Waking up and seeing that the site is already back up despite this all makes me proud and grateful to be on itchio.”
Point is that you can choose your own adventure in a way that eclipses fully relying on another company. Beyond that, you can choose to own as many layers as you want and stop long before building your own hardware and fiber network.
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.