I imagine part of this is just availability.

To use ChatGPT you have to go to their site log in and then use it.

A lot of people already have google stuff and are logged it already. You can integrate it with email and your google drive pretty easily. Plus they are really pushy with it if you use google for work. So it is quicker to access. Though can confirm it is pretty shit as I've seen the summary of a meeting I was in and it was not correct.

Gemini is technically already the most used LLM in the world because it pops up at the top of Google Search. Most normies don't care about the 'best AI', they'll just use what's familiar, and what's more familiar than Google Search?

Sam Altman is freaking out about how to deal with this.