I think a lot of people aren't aware of the difference between port and direct injection, and why it's important to have an air/oil separator (catch can) on a direct injected gasoline engine. Engines with any other injection method than direct injection don't "need" an air/oil separator. They will benefit from having one by keeping the intake and throttle body cleaner. But they are not needed. Direct injected engines do just that, they inject fuel directly into the combustion chamber. So there is no fuel to wash off the back of the intake valves and keep crud from accumulating on the back of the valves. Which can cause all kinds of problems. Poor fuel economy and loss of performance just to name a couple. This can happen in as little as 30k miles. Some manufactures like VW and Audi design an air/oil separator as part of the pcv system, which helps. But is not as effective as a catch can. And even with these systems, they still recommend doing a de-carbonization service at something like 80k miles. Some newer engines have a combination of port and direct injection, in an effort to see the benefits of both technologies. It seems to work pretty well from what I've read.
So I guess, to sum it up...the gasoline engines in our trucks are port injected. So we don't need to have an air/oil separator. But, if you want to keep your intake system cleaner it won't hurt to run one. Just make sure to empty the accumulated liquid periodically.