My Guess is that the environment is too bright to see the artificial light. 125 candela is about the same as a 100-watt bulb. If you turn on a 100-watt bulb in sunlight you won’t see much light in contrast to the sunlight. In real-world scenes, you will see the bulb itself illuminated, just not the cast light. The spotlight only represents the cast light, not the bulb so we aren’t seeing anything. You may test this by:
a) rendering with artificial lights only, or
b) cranking up the spotlight power dramatically to see if it shows up (note: this isn’t the recommended solution, just a test to prove the theory—and incidentally I tried this and started to see the light at about 1,000 candela)
If you want the light in the scene, I would add some self-illuminated bulb geometry.
I hope this helps.