The Euclid Alternative - S2-E5
Question: Though it comes up in other episodes as well, this one is focused on Sheldon needing a ride everywhere he goes because he can't drive, not to mention his not being welcome on the bus. Of course, this story element would be nonexistent if there was a simple answer, but it does beg the question: Does Pasadena not have taxicabs?
Answer: Sheldon DID finally use a taxi when going to the airport to see and propose to Amy in New Jersey.
Chosen answer: It does. The variable cleanliness of the cab and the habit of taxi drivers to engage customers in small talk would be too much for Sheldon to handle, and not an option for him.
Captain Defenestrator