Non-sufficient funds fees

This is not complaint, but want to know why ?

I was charged with $34 of "Non-sufficient funds fees". My a/c was having $2000 less for about 10 minutes may be, but certainly not a day or two.

If $2000 can earn $34 for 10 minutes - why bank does NOT pay me that rate of interest for saving a/c ?

What is the logic of charging EXCESSIVE amount of $34 as a "Non-sufficient funds fees" ?