what's wrong with spending it if you have it?
Nothing, but that isn't what people are talking about. Most people don't have the money and spend it anyways. Also, even if you have that amount in your bank account, do you really have the money?
Homes, kids, retirement, etc.
I think the "wedding cost hate" you see is that most people are aware that the entire wedding industry is a racket and there is a lot of animosity towards it. And everyone has "that one friend" who got married, spent way too much and either ended up divorced or broke afterwords. Most of this "hate" is just oddly directed advice and "warnings" to others.
This isn't hate against people who have a lot of money, it's hate against the industry.
I had a friend in Vegas who worked in production and DJ'ed on the side. He charged $100 to show up and $60 an hour after for a full DJ setup (lights, MC, etc), That's not to bad, but he charged $1,200 for weddings which last ~4 hours, Why? Because people would pay it.
Spending a shit ton of money on a wedding has become a societal norm, and it hurts young couples. Weddings were historically an event where family and friends came together to help a couple start their life, not an event where the couple gained $25K debt.
Nobody would ever bash a couple who made $200K a year for buying a $30,000 car, but people would be very confused if a couple who made $40,000 a year spent that much on a car. Friends and family would probably try to talk them out of it, hell, the dealer might even say it's a bit too much vehicle for their budget. But when it comes to weddings everyone not only supports that amount of spending, they fucking encourage it.
When my wife and I were planning our wedding we went to 1 wedding show, it was so awful. There were booths and people everywhere just like vultures trying to get our money. I almost lost it when a women wanted to sell me, and get this, "Smells" for my wedding. Fucking smells, it would have cost almost $2,000 for this service. You literally pick out a bunch of different smells, then you choose when (and even where) you want that smell "be" and for how long, then they set it up for you. They had these humidifier looking things that they would set up all around the hall, shit, they even up-sold you on what material and colors they would cover these things with. She even asked me if I had any "blind guests coming to the wedding, as this would be a way for them to share in our big day",
This is the shit people are bitching about.
Not the wealthy family throwing a $60K wedding. It's the plastic faced 40 year old women guilt tripping poor kids into spending a months salary on smells for great aunt Mildred.