I'm really failing to understand obsession with deriding people for solving problems that you personally don't have.

But yes, for some people it can be difficult to do this. It slows development, it makes programmers have to do sysadmin work (which in a two-person company without a specialised sysadmin can be difficult).

As another use-case, there was a point at which Twitter would take days or weeks to implement even minor schema changes across their entire MySQL cluster without impacting production.

And some people are solving problems that just do have unstructured or semi-structured data, rather than your assumption here that it's just a proxy for avoiding schema changes