Because most engines run pretty well with similar timing despite numerous variables. Unless it's turbo'd or supercharged, 16~20 base with 35 total should work for most setups. You have some pinging as-is, if you knew what your total timing was you might find the culprit.
You can figure these things out (timing; vac port used for advance, if any) with nothing more than a timing light. Driving it without setting the timing to some known quantity is a disaster looking for a place to happen.
You should be able to check base timing, and at what RPM the timing goes 'all in' as well. These are important factors. The amount of added vac advance is also crucial and can be measured.
Sounds like you have lots to learn, but you've found the right place to learn! Search, read, ask questions. It will all begin to make sense.