For some, a kid's happiness comes above all that until you absolutely HAVE to address those things (i.e. eviction notices or collections calls.)
That and in many ways, parents don't want their financial issues to become "real" to their kids. Ex: You want to keep Suzie in cheer at all costs because she CAN'T know how badly you're really doing. You want to do whatever you can to shield her from the consequences of your financial choices or the fallout from your hardship.
You can "hide" the collections calls and notices from your 11-year-old. You cannot hide the "your mom didn't pay for tuition" conversation or the "we have to quit cheer" conversation from her.
There's also an element of whether you've been THAT MOM at the gym. That Mom spares no expense on bows and practice wear, shells out for 3 privates a week, pays for 2 classes on top of tuition, springs for the nicer restaurants at out-of-town comps, etc.
You really can't go from being That Mom to telling your child "We can't do this anymore because we can barely pay our bills." You worry about what folks would say. So you cut corners with necessities, use your credit card until it's maxed out, etc.