I think that sometimes myths get created that make the creators and myth believers happy or feel better about themselves. These myths get created off a few outliers that help support the myth. So when someone is wishing their paycheque was bigger a handy myth can be consoling. Those IB people making all that money? Well, they don't save any of it due to lifestyle! Heck, even though I make 1/10th what they do I believe I save more. I'm probably happier than them too.
There's a quote that goes, "Comparison is the thief of joy." It can be but a real or mythical comparison can also make a person feel better.
THIS. Exactly. OP is kidding himself if he thinks FIRE isn't possible in NYC ibanking so he's better off not in ibanking for that reason.
Having worked in NYC ibanking and law, it's clear you don't understand the industry. You start off making 200k with bonus at least at/before your mid 20s. However, for the first 5 yrs in both industries, you are basically in your office nearly 24-7 working on spreadsheets (IB) or briefs/contracts (law). Very little wining and dining. You aren't wearing $1000 suits. Sure there are impressions being set internally, as the partners need to see you as someone they WILL one day put in front of clients -- so while I wouldn't come in wearing Target or Kohls clothing bc no one does -- when you make 200k+ it isn't that difficult for men to buy a half dozen pairs of pants at Banana Republic or the like and button downs; the women's winter uniform is cashmere sweaters with similar work pants from BR etc. You buy them once, dry clean them, they last a long time and you replace as needed. You don't have to spend thousands per yr or even $1000 per yr on clothing after the initial buying. You're in the office 24-7 so you aren't spending on food bc meals are expensed. You can live wherever you choose bc you're never home anyway -- you don't have to live in a luxury apartment.
Then 5+ yrs into your career, you get more into the "wining and dining" -- i.e. client development. In NYC that means taking clients to events, theater, fancy dinners etc. -- all of which is paid for by the firm including your car ride home at night. No one is coming to your apartment, so you can live wherever you want. Sure you may need/want to add a Brooks Brothers suit or two to your rotation but at that point you've made 200k or 300k+ for 5+ yrs.
Then IF you get to be a senior partner/senior MD who does a TON of the business generation for the firm, THEN you are going to be the one inviting clients etc. to your luxury penthouse or your house in the Hamptons. At that point you're making $1mil+ per yr in comp, so I'm fairly sure you can afford suits and a Mercedes. Reality is however, 99% of people don't get to that level. These careers are up and out -- not everyone gets promoted to the very senior executive role; along the way, many people are pushed out, leave for other jobs, leave for a different lifestyle that doesn't involve 80 hrs/wk, leave to move away from NYC etc.
As for why people in those industries don't FIRE -- same as other industries, they choose to spend. I worked with plenty of lawyers who lived LARGE -- luxury apartments; only shopping at Saks/Bergdorf; $1000 shoes for women; etc. They justified it as -- I'm a corporate lawyer, I HAVE to live this way to be successful. Reality is, ALL of those people became lawyers bc they had nothing better to do, did not want to do it, hated the work/hours/etc. so they kept themselves "happy" with the best things NYC offers. Some did not even have 401ks -- despite making 200k+ starting at age 25 and being single. Not surprisingly, their firms asked them to leave within 3-4 yrs bc they just couldn't handle the job. They still landed good salaried jobs at 100k+ or 150k+ and NOW in their mid 30s, they are focusing on 401ks etc. Sure you can save at 150k, but reality is it would've been a LOT easier to front load savings/investments when you made 250k.