Back decades ago.... my Dad was a cop. Dad used to say "Locks keep honest people honest".
Dad was right too. A lock can be like the proverbial "knife at a gunfight". Thieves come equipped with tools, knowledge, and/or tricks that are greater than any commercial locks available. But that 14 year old kid that doesn't feel like walking or taking the bus... who might steal your bike for a hoot. He can be defeated with a $5 cable lock.
Ride a beater... and when you absolutely can't be riding it... lock it up.