Why do only big ML labs dominate widely-used models despite many open-source pretrained models smaller labs could do RL on? [D]

The content questions why large AI labs dominate widely-used models like GPT and Claude, despite the existence of many open-source pretrained models of similar scale. The author suggests that Reinforcement Learning from Human Feedback (RLHF) is key to the superiority of these models and wonders why it wouldn't be more accessible for smaller labs.