Why are people’s interest sections so boring

I know exactly what you mean.

However, confession to make. My interests section is much more boring than most of my actual interests. However, I purposefully only post my normie interests as I don't want someone to have the wrong idea about the kind of person that I am.

For example, I have some really niche hobbies (think stamp collecting, making pottery, theater, etc.) Someone reading that my think respectively nerd, hippie, drama queen....not helpful to my interview process. Hence, why my interests are much more tame....running, jogging, etc.

In fact, I'm deep in the closet about my hobbies. Only a very rare few work colleagues know about them.

You list something that you can use to develop a dialogue with interviewers to demonstrate your conversational skills in a personable manner.
If there is something additional that you are also passionate about then bring it up during the interview. Not everyone can relate to unique hobbies and it occasionally misses the point.

(1) Most people aren’t all that interesting.

(2) It is an interest section on the resume. It is really just meant to demonstrate you are a human. Not everyone is going to be Taylor Swift’s roadie or will be on some youth national team. There are very few things one can put on there that are actually interesting

For the same reason most people's professional qualifications sections are the same - most people are similar.

And lets be honest, the people applying to jobs on Wall Street aren't exactly the most interesting bunch.  Most of the people I worked with had been trying to break into finance from the word go, which meant that they joined the same investment clubs, went to the same lectures, did all the same things as each other because that was the least risky path to getting a job, and people who want to be in finance are probably the most risk-averse people in the entire world (at least until they're gambling with someone else's money).

So no, you won't see folks who love underwater archaeology or something like that, because those people are naturally looking for jobs in those fields.  Funnily enough, though, the people who seemed to be most successful in finance were the ones who were least interested in it outside of working hours.  For an analyst or associate it didn't matter, but for senior bankers who needed to build relationships to drive revenue and business, being able to talk about something besides interest rate spreads or commodity prices seemed to really help connect with counterparties.  Shocking, I know.

Most people looking for a job are poor and poor people can't do interesting things because interesting things cost $$$$. You bet I would be very interested in yachting, polo, flying a plane, heliskiing if I wasn't poor. I would literally become the most interesting person in the world.

Think of it this way: how you gonna feel about an applicant who openly admits having the weird hobbies we all know and love?

* Building out my taxidermy squirrel army

* Digging tunnels under my yard to connect to the other local preppers’ nuclear fallout shelters

* Selling my proprietary smoked salmon recipe at the local farmers market

* Ghost hunting on abandoned properties

* Spamming Hillary Clinton’s social media accounts with disinformation

* Traveling to poor countries and taking cheap road trips, then posting about it on WSO

* Googling feet pics and selling them on OF

I took some chances with mine.  Mixed martial arts (university extracurricular on campus), where I was able to list out getting to instructor grade, teaching classes, etc. and the 6 months I took on leave to work at an orphanage overseas.  I'm not really sure how well those played out in finance though, and more recently I've been advised to drop them off the CV.  And at this point, both of these activities were decades ago.