They are users not developers. An academic or civil engineer who uses a CFD simulator usually has not enough programming knowledge develop such a complex application. The employer has not enough funds to pay for developers (see, they use a pirated software). Paying for developers is still more expensive than buying an already developed product.
Just look at the state of FOSS CAD software. There are some, but they are very-very limited compared to proprietary alternatives. Most people don’t care, they just want to get the work done. Not everyone is a programmer, even if it looks like that from our lemmy bubble.
My general view is similar, yaml is better if it should be written by humans, json is better if it should be written and read only by a machine. but hyprspace uses json for configuration, so I don’t really understand cellardoor’s comment