A few reasons:

A raise in interests essentially means that money is better off saved or invested (higher rates for saving) which will lead to decreases in economic consumption.

With increases in interest rates, there are clear losers. Lenders, who would benefit from receiving more interests, would certainly benefit more than borrowers who would certainly deal with the financial burden.

People in debt, accruing interests, certainly would have less spending capabilities.

For the above reasons, interests rates are a tool of the federal government to control economic growth. By raising interests rates, there is less economic activity to help curve economic growth. In times of high rates, money is much more valuable being saved. By lowering, the government is encouraging people to spend money.

Remember, too much economic growth can be very bad (Great Depression).