I believe it’s because of logarithmic growth.
If you have money in a bank account, it takes x time to double from 1 to 2. It takes x time to go from 2 to 4 and then 4 to 8. This exponential growth is scale invariant.
If I start at 5, it takes x time to get to 10. And it still takes x time to go from 10 to 20, so we’re still spending much more time with numbers that start with 1. No matter what you multiply by, you’ll always get more number starting at 1 in a sequence that grows exponentially.
Not all financial numbers are directly controlled by exponential growth, but the experts tell me the pattern holds. I’m willing to believe them, especially since this is a statistical analysis that allows for the occasional exception. (To rephrase that for clarity: if we say Greece’s numbers look fake, we can only say so with 95% or 99% certainty, or whatever confidence level we choose. We will never be 100% sure they’re fake because there’s always the chance that some set of true numbers do defy Benford’s law.)