True, foreigners are low value customers. We cannot participate in many profitable banking services.
And we are a thorn to customer service desks due to our need for english speaking reps. Then we accentuate the problem by approaching problems with a rude, entitled approach. I just witnessed an example today as a foreigner complained loudly that nobody could speak English to help him.
They get to use our deposits to make loans to Thai nationals but the value is still not that significant.
I brought my US social security benefits document. But they never asked for it. As you said they might be looking at your age and questioning the source of income.