Re: In this day and age no centrifugal section?
SpaceX's proposal didn't include a centrifugal section.
The real question is who is going to pay for a centrifugal section and why?
NASA wants the companies developing ISS replacements to fund at least 60% of development themselves. These companies aren't going to be doing this out of the goodness of their hearts. They are going to be looking to recoup their costs by leasing station space to non-NASA customers. Therefore we want to look at potential customers and figure out what they want and need.
Research done on ISS indicates there is a comparative advantage for manufacturing some products in microgravity. Drawing high quality fiber optic cable or growing replacement organs appear they will be highly profitable activities once the bugs are worked out of the production processes. In the case of drawing fiber optic cable vibrations from the centrifugal section are harmful to product quality so the companies attempting to bring this to market won't want a centrifugal section attached to their production facility. Manufacturers whose processes depend on gravity can get that for free here on Earth so we can't look to manufacturing to recoup the costs of developing a centrifugal section.
Another potential customer base is tourists. My informal survey suggests most tourists definitely want the chance to join the zero G club so a microgravity section is a must. Experiencing artificial gravity is something few are interested in. Having toilets and showers that function like those here on Earth would be nice but the costs would need to be tightly controlled. Developing and building a 100+ meter diameter centrifugal section isn't going to be cheap. Perhaps there might one day be enough demand to recoup the costs. For now all there is is speculation that does not justify the business case.