Social accounts are monetizable & part of peoples brands now - “well if it blows up ah well” might be fine for you or for me, but might not be for others.
Then don't use free instances? There's a bunch of companies that would run a dedicated instance for you for a couple dozen $/mo.
Less than that. Weingärtner is 4€/month for an instance they say is suitable for up to 5 users. Masto.host is $6 for the same. This is a major advantage over centralized social media in terms of platform risk.
Arguably we’re seeing the beginning of Twitter blowing up and if that falls to Digg-like irrelevance they face a similar issue.