...is the incentive to be legally creative. By which I mean the incentive to, at least within reason, throw an argument against the wall (or rather, the judge hearing your motion, which can actually be a lot like a wall, depending on the judge) and see if it sticks. Although you don't want to waste your credibility on a totally pointless or unsupportable argument, you do get the opportunity to make a long-shot argument based on a minority viewpoint and see if by some miracle the judge will decide you've been persuasive.
From what I've gathered about California criminal law, at least with 10 weeks at a public defender's office, is that for the most part, the law just isn't on our side-the 4th, 5th, and 6th Amendments don't mean what they used to, preliminary examination is just treated as a means to rubber-stamp a case for trial rather than a genuine opportunity to examine if there's really anything remotely resembling strong evidence...I could go on. I'm not totally 100% committed to staying in public defense, or even criminal law, but particularly when you stop and consider that, well, innocent people get accused of crimes sometimes (and even guilty people deserve rights, in a constitutional, adversarial system...okay, I'm pressing pause on my preachy tape right now), it's a little scary what some judges have become willing to let slide.
But all that is by way of saying that we have an incentive to try everything. And before anyone pipes up to say "Yeah, to bury the prosecution in a pile of paperwork! I see how you dishonest, criminal-loving PDs are!" (trust me when I say I actually heard this from someone I know. And it wasn't said with sarcasm, although I admit it wasn't said verbatim either), I don't get the impression that this is the primary incentive. Part of it is obviously the constant specter of IAC claims, particularly in capital cases. But more importantly, it's the specter of not doing all you can for a client. If there's a chance you could get a coerced confession thrown out, or the fruits of an illegal search suppresed, you want to take it, if taking it isn't such a long shot that your credibility is on the line.
And then if you're me, 1L Violent Felony intern, you get to write it. Which is so much better than law school writing. Why? Because your supervising attorney is not saying to you "that's a long shot, only a few cases go that way, you can't make that argument." I had a particularly frustrating 1L Moot Court experience-I had an interesting problem, and enjoyed oral argument a lot, but my student editor was one of those unhappy folks who wants to make everyone else unhappy too (a popular species in law school). If you tried to come up with an argument that hadn't been what she imagined when she wrote the problem, you were shot down-"that's a long shot, the judges won't like it, there isn't enough case law in support, you don't understand the issues (even if you did) because you are a lowly 1L who couldn't possibly have original thoughts and it is not physically possible for you to come up with a good idea I didn't think of first..." (okay, so that last part was just implicit). Now, quite possibly the incentives are different in other practice areas. But for now, I'm happy to have spent the summer working on assignments where the incentive was to try anything you could think of. Because it's nice, after a year of law school, to actually get to think of things.