It's not necessary for it to be a general purpose programming language, though. I think it is kind of neat to have a very specific, personal language that fits

It's not necessary for it to be a general purpose programming language, though. I think it is kind of neat to have a very specific, personal language that fits your mental model. On a larger team, probably not what you want, but there are other languages that are optimized for that. Basically you're right if the creator wants a widely-adopted general-purpose language. But there's other valid approaches I think.