Pointless Petition du jour: The meaning of inauguration oaths taken by public office holders

Secular jihadists have set their sights on the inauguration oath typically taken by many public office holders.  Here is a new petition -- undoubtedly inspired by the Kim Davis kerfuffle -- at whitehouse.gov:

I think it's worth pondering the purpose of inauguration oaths.

The whole point of an oath is to increase the credibility of a promise. The oath-taker is essentially calling judgment down upon him/herself if the promise isn't kept.  When the oath-taker is considered to be sincere in such an oath, it generally adds weight to the promise being made.  If the oath-taker doesn't believe in a higher power, the oath is pointless both to the one doing the promising and to the one being promised.

In this light, swearing on the Constitution (as the petition demands) is even more pointless, regardless of one's belief system -- what does "I swear by the Constitution that I will obey the Constitution" even mean?

Image source: Bizarro

The real issue is not that many people prefer to add meaning to their oath by placing their hand on the text that underlies their moral value system; the real issue is that the oath itself is effectively meaningless to the oath-taker.

At one time, the inauguration oath served a real purpose in a culture where the moral value system of Christianity served as an actual constraint on the behavior of the citizenry and (in many cases) public officials.  Now that Christianity is being systematically purged from the culture, even pro forma declarations of religious sentiment among public officials are becoming less common.

So, again: is there any point to inauguration oaths any more?  It's not like most oath-takers are actually sincere in the affirmations being made (or fear any repercussions of violating those affirmations), so why undergo the ritual in the first place?