Edit: before folks reply with a comment about people being worse off, I know. I agree. This is just a scenario description.
It is very easy to be strapped with a modest sized house or apartment in the "right" zip code.
As in a 1.2mil mortgage on a 3 bedroom house that's never been renovated since the 70s. That mortgage could be 5k / month.
150000 a year is 8.7k a month, after taxes. If you have student loans, any medical debt, kids, that remaining 3.7k is pretty critical. You aren't swimming in liquid chocolate every night and wiping with singles.
If you own a home things can happen out of nowhere. I personally just had to replace my sewer line last month. 17k for the work and 1.5k for new concrete. Not covered by my home insurance because I didn't opt for the rider on my account. My fault there... My finances are a bit different than the above description but if you were the 150 + paycheck to paycheck situation, you'd be in hot water.
This isn't a "woe to the 150 crowd" comment. I'm well aware folks are way, way worse off, but when a 150 household talks about being paycheck to paycheck, it's totally possible.