Thank you. This happens all the time. From Fran Vazquez, to Thiago Splitter, to David Andersen, to whoever the fuck else you want to throw in there, guys get drafted and don't come over right away all the fucking time.
Once it came out that Rubio would have to essentially play for free, or even pay to play, sending each paycheck to his old team for the next 2 years, many people began speculating that he might not automatically come over.
It was already expected he wouldn't play for Memphis, so him not wanting to play for another of the NBAs most moribund and hopeless franchises does not surprise me in the least.