Why do people say for example it's eight o eight when the letter o is not a number? why don't they say it's eight zero eight?

The number zero looks like an o (0 and O) so they say "o" instead of zero
and it's easier to say oh than zero
lol

Hope this helps ;)

It is because it is much easier to just say o clock instead of zero clock. Its the same with addresses instead of saying 6 zero 2 street its 6o2 street