In theory, Bonus is a means of paying smarter, harder working people a higher wage per hour.
When implemented, "bonus" was nothing more than a cash bribe that was paid for falsifying your timecard and indicating that you took a lunch when you did not.
This allowed the company to pay straight time for hours that should have been compensated at the overtime rate. It also allowed the company to avoid making pension and health&welfare contributions for those hours.
It also gave the company the ability to dispatch fewer vehicles, wheich meant fewer drivers, which meant fewer benefit plans to fund.
Even people who didnt want to be "bonus" drivers were effectivelty coerced into working off of the clock because if they were filling in on a "bonus" route for someone who routinely skipped lunch, the only way they could possibly maintain the same level of production was to skip their lunch too.
"Bonus" is and always has been a scam and if you have an opportunity to get out from under it then by all means do so.