Mainly to prevent inflation from getting too bad. We've got very low unemployment (among those actively looking for work) and still have excess amounts of capital sloshing around combined with the tax breaks. They're trying to keep the economy growing at a steady pace instead of taking off like a rocket only to crash land later.

To reduce the heat in what could be an overheated economy. Many economists look at the employment rate as being too low which could signal inflation.

This confuses me a little. Many things seem to be pointing towards inflation - worsening global trade climate, high employment, knowledge that economic difficulty will be met with printing etc. But if the market expects inflation then shouldn't long term rates be higher to offset the expected inflation?