I've been told that there are people who trade their cars in when the tires are worn out - it kicks the payments down the road a month (they have to budget next month lower than this month, but it doesn't use cash they don't have) Remember, nearly anyone can get a car loan no matter how bad their credit is. Even a credit card has higher standards. Since we are talking about people who are bad with money it is at least believable.
Had a 14 year old car... 225k miles on it... a couple years ago had put in $1k or so, but the last 18 month had put in less than $500 in repairs (tires, oil changes, some other issues).
However, there was an oil leak, and some damage to front-end suspension. Oil leak had been going on for a while, but getting worse. Finding it would have meant taking the engine apart, and the front-end stuff was also expensive. Even without the engine leak, I was looking at probably $1500 to get this to pass inspection this year, and... there's no guarantee that all the fixes wouldn't have left me with something with a broken transmission that needed an overhaul or replacement. Fixing it all would probably have been north of $3k to feel good that it would be road worthy for at least another few years.
As much as a I hate change, I bit the bullet, and got a 'newer' car for $11k. 'used' but still relatively new (2016) and it's far more fuel efficient - getting around 40mpg vs the 25 I was getting before. The fuel efficiency won't totally make up for the entire diff in fixing vs replacing, but I have something that's more modern, more comfortable, gets better mileage and better safety features. The 'brand new car' comparison - yeah, but loads of people are fine getting a 'lightly used' car vs 'brand new'.
A friend went through similar decision within 10 days of my process, and he ended up getting a lightly used car (2017?) but it was $21k - I just can't bring myself to pay that type of money for a car right now. I was looking sub $10k; my wife pushed me to go a little higher.