The only one I’m familiar with is that you drive more than you report and that lets you take on more jobs. You’re not supposed to drive more than (for example) 14 hours / day for safety reasons but most drivers that pull six figures tend to have violated these laws fundamentally.
It may not be to take more jobs, it may be to keep the one you have. Say it takes 14 hours and 45 minutes and you can only log 14 hours drive time. How do you get the job done when dispatch is promising you'll be there? Start driving before you log the start of your day, log breaks when really you've been peeing in a bottle, log some time to inspect your truck when you are stuck in traffic. A little here and there. You can also fudge when you slept and start so you can get rolling sooner. The pressure to do this is huge. If you won't, someone else will, so you do it to keep your job.
Bonus, if you are caught the company doesn't care, they will hire someone else, but it sticks with your record.