Depends on your operation....
If you're running a medium size company and have a large truck and 18" or bigger chipper with a full time crew, then it just doesn't work out to be worth your time to mess with firewood. Some guys do it on the side, if they have land... and use the down time of their crew to split and stack, or mostly to give the crew something to do in quieter times in winter (delivering wood). You obviously need to have land though. For myself, I chip everything. Trees up to about 4'~5' in diameter get ripped and chipped. It's quicker than you might think. I don't get may trees over 5' any more, and when I do I price them high enough that I don't win them.
If you run a small time show and have a small chipper (or no chipper at all) then how you get rid of wood becomes a different story. Most of these guys have plenty of time, and their time isn't worth much. They may chip the brush if they have a 9" chipper, and try to give away the rest as firewood, or convince the owner to keep it. If you don't have a chipper at all, then you're probably loading it all on to a trailer and slashing it up which is very time consuming. You're then either taking it home and burning it in a big slash pile, or paying to dump it. Either way, getting rid of it as firewood (even for free) is going to save you money. You're wasting a lot of time dealing with the wood this way though.
To put it into perspective, a small crew and truck/chipper needs to bring in minimum $2000/day. You can chip most big trees in an hour or less, the whole lot. Which means you can crank out 2 or 3 jobs a day without too much effort. 3 good size jobs might bring in $3k~$4k for the day which is a nice profit. If you've got the crew there, sawing, splitting.... it's all money lost. If you're running a one man band with a trailer, you may not have a backlog of work, or a lot of 'by-the-hour' costs, so if it takes you an extra half day to get rid of the wood but saves you some money, then that day was more profitable for you. Pretty tiring though.
Shaun