> SpaceX will not attempt to land Falcon 9’s first stage after
launch due to mission requirements.
Could anyone knowledgeable about the topic care to explain the rationale here?
For this launch, the rocket will need to launch a very heavy satellite (up to the rockets performance limit) to a higher altitude. Thus requiring all of its fuel. There won't be enough fuel left to land the rocket since they need to bring velocity back to 0. Weight matters a lot too (even the coat of paint on the rocket adds up) so having no legs would increase the performance of the rocket.
How common is a payload of this weight?
They're not uncommon but SpaceX doesnt see most, there are other higher-performance launcher platforms that can easily put these into orbit. SpaceX's next rocket (Falcoln Heavy) will roughly quadruple the capability of their platform. The other SpaceX limitation is their fairing size. They designed their rockets to fit under bridges on American highways which limits the size of the payload they can deliver.
I think this is the case if the mission fuel requirements are too high (if they want to get to a higher orbit for example), then they won't have enough fuel to do the correct burns to land, even on a drone ship. Notice that they're not even including grid fins or landing legs to minimize weight.