There obviously is disagreement, even among experts. I cited not only veterinarians, but also well known animal activist groups like the
animal humane society.
Of course, some disagree with that, too. But I don't think it's obvious there should be no disagreement. What you refer to as "vanity" others would refer to as "cost." One of the primary benefits of a cat over a dog or other pet is low cost of ownership, and clawed cats can sometimes significantly reduce that benefit. For some people, that isn't just a benefit of vanity, but one of necessity. Further, even if it is not technically necessary, I don't think people should be considered cruel because they don't want to pay lots of money to keep their pet.
For example, if people are told they need to pay 1,000 to perform a procedure on their dog, they often choose instead to put it down. That is completely reasonable and acceptable, because we often have to choose to kill our pets rather than pay for them.