It is much easier to understand when you realize that it is often product of long process and not someone just saying "we want to make new language".

It usually starts with the idea that some problem can be solved using a simple domain-specific language. The intention is often to have non-experts use this language, so it is simple and often lacks features like strong typing and modules.

So far so good. But then, people start hitting problems that cannot be solved by the language. So new "features" are slowly added to solve those problems. And as the process is slow and features infrequent, there is no motivation to design those new features properly, as long as the problems are solved.

Over time, the new language gains features that turn it from a simple domain-specific language to a complex "general" purpose language, often with conflicting, confusing semantics and hard-to-follow syntax rules.

And by the time people realize they created such massive beast, it is already too late to kill it and replace it with a properly designed language.

There are a few languages that evolved like this that are not bound to specific companies cough JavaScript cough PHP cough.