Because Google keeps canceling projects and refusing to release products. Google invented the concept of transformers which is what the T in GPT stands for and then never did anything with it for years. Just last week Google published their PaLM-E paper in which they re-trained their PaLM LLM to be multimodal including the ability to control robots. Before the paper was even published Google did what they usually do with successful projects and shut down the Everyday Robots team that developed it.