With all of the ignition timing questions, why not use a timing light?

[oldbike99]

Other than the trouble of finding an old timing light that will work on our cars, is there a reason that more people don't time the ignition that way.
Once the pulley is accurately marked and a timing scale is installed, ignition timing is so simple.
No more question about "what is what" with lever position. Also, one can have a repeatable baseline to work from when experimenting to find what works best with your engine and fuel
Am I missing something?