One big one is that today's parents put too much pressure on themselves (both individually and as a group) to always be supervising. Some parents don't feel that they can leave their child alone for 30 minutes while they shower or clean, or watch TV, because we've built up expectations that everything is structured and that we're supposed to sacrifice our individuality for the kid. Some recent research has shown that millennial parents are spending a lot more "hands on" time with their kids than any previous generation, rather than passive supervision like when kids are playing in the house while the adults do something else.
Plus there is a significant line of people who feel compelled to do high effort, high visibility shows of parenting effort: Instagram worthy birthday parties, more structured play and learning, high effort cooking of things from scratch rather than convenience foods, etc.
Finances (and working hours) are definitely a big part of it, but a bigger part is the shift in norms and expectations that we're expected to be much more for our kids than prior generations.
It's easy to point at social media, and that's part of it, but I think it's probably the ubiquity of photos and videos, easily transmitted to others. Even those of us who aren't on social media still send photos and videos of our kids to the grandparents, to cousins, to other friends and family. We're constantly exposed to parenting highlights, which subtly shifts the expectations on what the non-highlight portions look like.