As an early IT job, I worked for a famous boxing promotor who would take end of career fighters and charge them a fee to "school them" into bodyguards and find their first quazi-celeb client. Was fascinating to watch their training at the gym.
Basically, most fights are fixed except for big headline bouts. Trainers and promoters can tell from the start whether you're a potential contender. If you are, they're not going to let you get your clock cleaned before everyone's getting paid. If you aren't, the only thing you're good for is building up another fighter's record.