How many other drivers have entered or returned to F1 at his age and with so many years not being an active F1 driver? None. How many had returned with debilitation from a life threatening accident? None.
I would assume that Vettel’s comments were taken out of context and the question he answered was more complex than it appears.
Remember this is media scavenger season.
It's certainly true that we have to take the quotes from F1 journalists with the proverbial 'pinch of salt'.
All the same, an F1 driver's job is to create attention for the team sponsors. The best way to do that is to win races, but I think we can all agree that it doesn't matter who Williams hires, they're not going to win. So the next category for creating attention is being a driver from a country without other drivers. Poland is a large country with very little F1 presence, so if not Kubica, who else would it be? Even if there is another Polish driver with the skills of Kubica (which, it's a big country, surely there's a few talented drivers), who has the story that Kubica has to tell? Williams (and their sponsors) are going to be the darlings of F1 coverage as the season begins. And if Kubica does have success? He'll be the F1 story of the century. And if he underwhelms? Then there's room for a younger driver to take his place.