Why do we have Debt ?

On the surface it appears we have debt because we want to spend more for government than it generates. But who decides what government will spend $ on and why tax rates are what they are. The rational doesn't make any sense to me and to most people I speak with. It seems in most of my adult life government has run a deficit. It seems politicans want to reduce tax revenue and give tax money to entities. For some of these entites what they receive in tax revenue business is far and away more than they supply in tax moneies.
For me this is the central problem.
There is also a more significant issue in play. In the 40's,50's, 60's & 70's  if one wanted to make money one went into the private sector. Since Reagan business as moved to take over government. By now its hard to name a corporation that doesn't have government 'business'. They seem  to provide inadequate, incompetent service, over-priced products & services and constantly demand to pay less and less in taxes at the same time.
Now we are at a crossroads - the idea of being an individual citizen in america has become a myth - the new definition of citizen has come to be a corporation or the interests of the '1%' as well as the top 5% (?). Political office is viewed as a way to become rich This is the central problem with the voter group - electing individuals who don't serve the voters interests or more clearly - the voters don't seem to know their own interests.