Answer: It helps convey how jarring it was for Didion to realize that life in New York City, which she had long imagined as a romantic and exotic place, could be rather ordinary and mundane.
In this excerpt, Joan Didion conveys her experiences moving to New York. Before she went there, she had imagined that the city was a place of dreams, and that it held something exotic and special. She failed to realize that for many people who live there, New York is simply another city where they live common lives. She mentions buying a toaster and installing cabinets as examples of common things average people do, and which are not exciting or dreamlike.