Presidential Campaign

I have a question regarding a sitting President campaigning to keep his job. A sitting POTUS has the ability to have a presser on a moment's notice to discuss his policies. A sitting POTUS has the ability to ask any media outlet for an interview where he can discuss policy. A sitting POTUS has the ability to jump on Air Force 1 and travel to any part of the country for "important" visits to talk about his policies and initiatives. A sitting POTUS has numerous PACs which will carry his water and spend millions on political ads. A sitting POTUS has the ability to absolutely control the news cycle.

If a sitting POTUS has done a good job and has delivered on the promises he made to get elected, why does he need to spend hundreds of millions of dollars to campaign to keep his job? Why must a sitting POTUS spend millions of dollars trying to demonize his opponent? Shouldn't the job he has done the first four years be his biggest asset when it comes to seeking re-election?

A sitting POTUS has a tremendous edge in an election for a second term. Why must we, the taxpayers, pay his salary for running the country when in essence he spends most of his time running for re-election? Why must we, the taxpayers, foot the majority of the huge cost for him to leave D.C. and wander around the hinterlands in search for votes?

Regardless of the party of the sitting POTUS, I find it amazing that we, the taxpayers. don't seem to have a problem with this whole re-election process. Doing a good job, being a good leader, and delivering on promises made, should be the ultimate campaign tool. Spending hundreds of millions of dollars to convince the voter that what they have seen for the last four years isn't a portent of what will be realized for the following four years, is beyond outrageous. Either a sitting POTUS has done a good job or he has not and that should be sufficient "campaigning" considering that he owns the bully pulpit. What am I missing here?