Truckers perdiem is different from the rest of the world that gets perdiem.
In a nutshell, it is a company will take a certain percentage of your pay and make it non-taxable. So the actual benefit is tax money saved which is peanuts. They'll still get their regular paycheck plus about $30-40 in saved tax money.
Come tax time, you are allowed to claim 80% of $59 a day. You subtract what perdiem you were already paid on your paycheck and get the difference.
Whether they claim perdiem or not, you still get the same amount tax time. If you don't take it during the year, that $30-40 a week you'll see on your tax refund.
If a driver has a choice, it's best not to take it as it lowers your social security, lowers your 401K, lowers any workers comp or unemployment benefits and appears to everyone that you made alot less than you actually did. That might make a difference on a loan or a long term disability claim, etc.
The way trucking companies do it saves them money as it reduces all the matching they have to do on medicare, 401K, workers comp and unemployment payments. That's why some companies force drivers to take it. It saves companies thousands and thousands.
Look up at the forum toolbar, you will see "search" between new post and quick links.
Type "perdiem" in there and you'll find a bunch of threads on perdiem.