It's the same reason people like Jeff Bezos spent 250 mill a decade ago on the Washington Post.
And Musk spent 44 billion on Twitter.
Words matter - words can change the world.
Sure, harmless now, but imagine you let one of these LLMs actually use your browser, logged in as you, and it does something that you didn't intend it to do. We are getting to that point fast where you can ask an LLM to check your emails and answer them for you, order food from uber eats or use some internal company or government system that can control a huge number of different variables.
Funnily enough it seems human error (through bad or misguided LLMs prompts) is going to become much more common as LLMs do more things for us. You would kind expect the opposite from automated computer systems, yet here we are.