That´s not actually the case for the United States, if you look at government spending carefully, it´s actually shrinking as a percentage of the total money supply. People who like to claim that it´s growing, invariably fail to factor inflation and/or money supply growth into their charts.

The actual answer appears to be that it´s being squeezed into the financial sector by several positive feedback loops operating around lending, and in particular securitized lending - but that´s not the sort of answer that helps to pander to populist sentiment, and securitized lending is a trillion dollar industry - so you won´t see it discussed very much.