That is because the deficit spending problem escalated slowly starting with Kennedy, Johnson, Nixon, Ford, Carter. Escalated with Reagan, Bush, Clinton, and the first 7 of Bush's years. Then went full on insane in year 8 of Bush and each of Obama's.
All that adds up to $16+ trillion in debt. More than a years worth of GDP... and it doesn't even begin to address the massive underfunding of Medicare. The balloon was being blown up by our parents and currently we continue puffing away. Eventually it will explode. My guess is that it will be on the echo boomers and their kids. Unless we do something about it. $11 Trillion or so in the past decade is what we have added. It is our obligation to pay that back in the next 15-20 years with interest (at the longest). We will never accomplish this (obviously) if we continue amassing $600B+ in deficit spending every year for the foreseeable future.