When our daughter was little, we had neighbors with a daughter about the same age, and sometimes the girls would play. Our daughter had been really good all the way around, getting straight A's in school, being kind, never asking for anything significant, etc., so that year we decided to splurge and get her an American Girl doll for her birthday. If you don't know, those were dolls that were stupidly expensive and were all the rage in the early 2000s. We weren't wealthy but it felt like she deserved the splurge and we knew she'd take care of it and have it forever like all her toys (she's 26 and still has it in great shape).

She loved it and everything was great until the neighbor came over the next day, absolutely livid. He wanted to know why the hell we had to get our daughter an American Girl doll. I was just totally confused, trying to understand what the issue was. He angrily said, "Now we have to buy our daughter one, and we just can't afford it!" I didn't know what to say. Were we supposed to ask them what they could afford and only buy our daughter those things?

They bought their daughter two of them so she'd have more than ours did. Ours was really happy that her friend got two of them, and it didn't even seem to occur to her to want a second one - she liked the one she got.

People are weird.

Middle-class suburban streets, miles away from farm or forest, full of sparkly clean gargantuan pickup trucks

I'm going to go with a slightly unorthodox answer. Phones.

You don't need a new phone every year. You don't need a new phone every two years. You don't even need a phone every three years. Your old Galaxy S7 or iPhone 6 still works. Don't waste your money keeping up with the latest phone. So what if it has a slightly better camera? What are you taking pictures of? What does it really do that your old phone doesn't?
Once you properly consider everything you realise that you only really need to upgrade your phone every 4-5 years minimum. Many will last much longer.

Girlfriend's sister and her husband were essentially homeless. Buying computer equipment and streaming gear they couldn't afford while living in her parents basement.

Their close friends had a child. Girlfriend's sister and her husband had a kid to be like their friends. Total disregard that they were living in her parents basement, not to save money or to buy a house, but because they lose their jobs so often they had no other choice.

My mistress insists on having as nice a house as my wife, like wtf?

Apple products.

My personal favorite is the Christmas decoration wars.

People who drive trucks to get groceries, bonus points if the truck is lifted

Can someone explain what that slang means?

Every single aesthetic feature you see anywhere is the result of this.

It's why we have grass lawns and consider our "fancy" clothes fancy.

Some rich fuck decided to flaunt their wealth and a bunch of dumbass poor people started doing it to

Anything to do with iPhones

I was recently able to take my kids on a big trip to California to visit family and take a trip to Disneyland for the first time, and I could really only afford it thanks to the generous financial support from family, especially since everything ended up costing us at least twice as much as we'd budgeted and saved for.

My brother in-law who's in his 40s recently settled on getting back together with his ex-wife after lots of disastrous relationships (and their relationship was very disastrous too) and he's constantly getting bailed out by his mother on basic household expenses due to constant impressively bad short term financial planning. He works at a factory making decent enough money which he could live off of with some basic budgeting (aka not spending literally all of his income on tattoos, piercings, music and alcohol) and his ex-wife who has her own host of issues works at a fast-food restaurant.

They told us that they're going to take their kids to Disneyland in California next summer, and also tried to test the waters for inviting themselves to stay with my family. I suppose they can't get much worse off financially than they already are so I should be happy for their kids of they manage to pull it off, but holy crap was it an obvious attenpt to one-up us