In some cultures giving money is expected as it's good luck.
Chinese will give ung pao (little red envelopes)...we got red envelopes from my Wife's aunts and uncles in exchange for a cup of tea during the tea ceremony. It seemed like a good deal to me.
We then had to give money to the children at the wedding.
My older brother was a bit peeved as he had to give us money, which we then gave to my younger brother. It was quite comical seeing my 29 yr old 6'+ 15st younger brother sat in a line with a bunch of 6 year olds waiting for their red envelopes.