I agree with Riley, it depends on the situation.
I was raised in a house where swearing was allowed. It felt normal until I went to friends' homes. I learned really early to turn it off at school and in front of other adults. I remember letting something slip on the playground in third grade and my friend said she was going to tell on me. There is nothing worse than having a mom who COULD NOT turn it off at school, especially when she was called in about our swearing or bad behavior. That was embarrassing.
I do not cuss regularly, and ironically am a teacher now. I have learned the great art of turning it off ---until I'm around my family in a stressed situation---and still am pretty good of turning it off around any children.
I will not allow my children to cuss. I do think it is looked upon as trashy, something I don't want to live through again.
I think the cussing and overall untidiness of my appearance (and smell of cigarette smoke) kept me from having the best school experience I could have. I didn't have many friends until middle school (when I realized I had some control on how I looked, smelled, and acted).
Lazy parenting on my parents' end? Yes and no. I realize now as an adult that they were overwhelmed with life. Mom worked full time on second shift. We didn't see her until the weekends. Dad was/is an alcoholic and treated Mom terribly. He was/is self-absorbed. His needs and wants came/come first --- I don't think he knows any other way. We had lifestock and a large garden. They struggled financially all of the time. There were 4 of us (3 boys). That's not easy no matter how you slice it. I think they were overwhelmed and did the best they could. The interactions with us kids were only of an evening (my dad being the caregiver ----very hands off) and on the weekends when dad disappeared on the property and mom tried to put the house back together, do laundry, and get groceries. There was lots of fighting among my parents and among us kids. My parents were never proud of our behavior -- just overwhelmed and uneducated on the best approaches to parenting.
The difference, I think is that my brother and SIL parent similarly to the way my parents did it, BUT encourage the swearing and bad behavior. They may have more money and dress the kids to the nines and give them anything they want (including age inappropriate items), but they encourage bad behavior and think it's funny that the 5 year old cusses and tells the teacher off. They retell the story in front of their kids to anyone who will listen with a sense of pride. They left the 2 year old twins in their strollers and car seats for most of their life. I could go on and most of you on here have read my posts about this family, so I will stop.
I know you are looking at the parents to blame, but remember you have not walked in their shoes or see everything that is going on in their world. I'm glad you are not looking at the children. Until I became older, I didn't know any better.