Authors publish papers on research, experiments, findings, etc. They do not always release the code for the models they are studying.

The lucidrains' repos implement the models, creating an open-source implementation for the research

The next step would then be to train the model, which requires a lot more than just the code (most notably, money). I assume you're referring to these trained weights when you say "the needed AI model". Training would require a huge amount of time and money for a team, never mind a single person, to train even one of these models let alone a whole portfolio of them

For this reason, it's not very reasonable to expect lucidrains or any other person to train these models - the open-source implementations are a great contribution on their own!