Also, why is the answer always raising taxes instead of decreasing the amount spent?

Because austerity has a negative impact on private sector growth inherent to decreases in federal spending across multiple sectors.

For instance, let’s say you decide to attack the debt via austerity by slashing SSI. If you do that, there is not only a decrease in federal spending resulting from cutting entitlements, but there is also a mirrored decrease in private sector revenue and growth because old and disabled people have less money to spend on goods and services. This, in turn, also results in declines in tax revenue generation because: a) companies that would benefit from government-generated income streams see lower sales, and thus pay less in taxes; and b) people are spending less and thus paying less in sales taxes, etc.

Here is a good work about it I used for an article once:

http://journals.sagepub.com/doi/abs/10.1177/002795011222200109