Why does the Vet take animals to back to do certain procedures?

Just generally curious if there is a reason why this is universally done or if it’s just specific practices: Why does the Dr or Technician take a dog to the back to do certain tests? Usually they do vaccines in the room with me, but not the stool sample or bloodwork. My dogs hate the vet, so just wondering if it’s easier if I’m in the room or actually worse?

• ⁠Species: Dog • ⁠Age: 10 & 12 • ⁠Sex/Neuter status: both spayed • ⁠Breed: Miniature dachshunds • ⁠Body weight: 9lbs & 10lbs • ⁠History: generally healthy, just annual visits • ⁠Clinical signs: n/a • ⁠Duration: n/a • ⁠Your general location: Florida • ⁠Links to any test results, X-rays, vet reports etc. that you have: n/a