Chat based LLMs are not about doing serious work (I might even argue LLMs in general are not suited for serious work). I much much rather have my LLM "assistant" as flawed as it is with me all the time than be tethered to a computer
I do coding on mine which to me is serious work. Not vibe coding, more like pair programming. Anyway, I'm saying "why not both?" desktop and mobile, not one or the other