Who gives a fuque? "Swearing" on a book is a meaningless and utterly irrelevant relic of the Stone Age. For all it matters she could "swear in" on a Sunday comic section of the Cincinnati Enquirer from 1946. They ain't swearing to read a book -- they're swearing to do their job.
Therein lies the problem.
Not too awfully long ago swearing an oath of office meant something. It was a person swearing an oath to carry out the duties and responsibilities which they were tasked with dutifully and faithfully. It was them saying I vow to do this, and you can trust me.
When you swear in on something that means nothing then your oath means nothing. If you swear in on something important, something that is a foundation of your faith and a belief / foundation that has helped you develop into who you are it means (meant) something. It WAS the person declaring, "I swear on this document, that has helped make me who I am and that helps guide my steps / actions in life, that I will........"
As you point out, though, taking the oath of office, swearing in, has become equivalent to useless ceremony where those 'swearing in' are like, "Yeah, whatever...I intend to do the job....'
IMO, it was Barak Obama who became the 1st President in US history to lay waste to / render the Oath of Office / swearing in ceremony' a useless sham.
He obviously meant NOTHING that he said during the swearing in ceremony, as within a few days he publicly violated one of the very things he had just vowed to do by declaring publicly that he was ordering his (criminal) US AG NOT to enforce a Law passed by Congress because HE did not agree with it. For the next 8 years Obama violated both Constitution and law while aiding and abetting this nation's enemies and victimizing the American people through the trampling of their rights again and again.
But again, the act USED TO BE a person swearing on something they held dear, something they valued, that helped set their founding ideals and beliefs, that helped them to become who they were, something that helped guide their decisions and steps. As you pointed out, it has become an un-respected joke.