Nobody loves an uncomfortable conversation about an overweight pet.

From Phys.Org, "Many veterinarians aren't comfortable talking about fat cats."

I don't think you can really point the finger at anyone here! The only solution seems to be making sure everyone understands that obesity is a legitimate and serious health concern for cats, meaning a) veterinarians and vet nurses shouldn't soft-pedal or tap-dance around that fact, because they're doing a disservice to their patients when they do, and b) cat owners should understand that when the subject is broached, it's only out of a sincere desire to ensure their pet lives as long and healthy a life as possible.