My modern car recommends synthetic changes at 7,500 miles by the book. Sending off samples to the labs, it looked good at that point but started to get some bad degradation at about 11,000mi. It would be sludge a little after 15,000mi and would have probably destroyed the engine before 25,000mi
Oil analysis is about the cost of an oil change for most people and sometimes says change the oil so most people just change the oil. For some it makes sense to do oil analysis.
Otherwise you're talking about extremely rare one-off cases where someone's car happened to be in just the right environment and built just perfectly the whole time. I'm not talking about "that one time one guy in a forum five years ago said his car lasted 120,000mi without an oil change", I'm talking about normal advice for normal car drivers.
