| Quote #1
Over the table, on which an unpacked line of fabric samples was all spread out – Samsa was a traveling salesman (1.2)
We don't get many details about Gregor's room, but the few details that we do get suggest that Gregor has very few extracurricular activities. He's a man devoted to his work and not much else.
| Quote #2
"Oh God," he thought, "what a grueling job I've picked! […] I've got the torture of traveling, worrying about changing trains, eating miserable food at all hours, constantly seeing new faces, no relationships that last or get more intimate." (1.4)
The life of a traveling salesman should look awfully good to someone who just got turned into a vermin, but that's not the case for Gregor. Gregor views the transient life of a traveling salesman as, well, dehumanizing. It's an asocial and physically grueling lifestyle.
| Quote #3
He was a tool of the boss, without brains or backbone. (1.6)
The inhuman aspect of Gregor's job is emphasized here. You could say it's worse than being a vermin: Gregor is reduced to a mere, inanimate "tool."