As you said though, that is their job. They protect the people because they are required to do so. I don't see why they need to have a reason to do their job other than they want to get paid.
That's not a very good reason to cheer for them, and like I said before, it doesn't explain Keiichiro's extreme hatred for the thieves. If all he cared about was doing his job, upholding the ideals justice, or getting paid, he wouldn't go all Zenigata levels of angry when he sees them. Capturing the thieves would just be part of the job, no different than filling out paper work or anything else. But that's not the case. His anger is a PERSONAL grudge, one that has gone unexplained. You can't have it both ways, either all 3 PatRangers have a personal stake in this or they don't. And "it's just our job" might be an okay excuse in another show, but you're suppose to pick a side and cheer for them. The show's tagline even says "Whose side are you on?!". Kind of makes it hard for any audience member to cheer for the police if over half of them are emotionally unattached because "it's just a job" and only one of them has unexplained outbursts of anger. After all, they are more than just cops, they are suppose to be super heroes too.
In DekaRanger, it works because the characters genuinely believe in the justice they are fighting to protect and uphold. They've seen innocent people get hurt and killed, and it drives them. In Lupin VS Pat, there may be a sense of duty, but there's a lack of conviction from the police.
When Zenigata gets angry at Lupin III, it's because he's stopping international super thieves, and he hasn't caught them once in years. He's still trying even when many others have given up. Even if the Japanese police branch has stopped caring that much about Lupin III, Zenigata has all ready wasted much of his life trying to bring him to justice. It's personal.
But here? I understand the police wanting to stop the Ganglers, that's just par for the course of a super hero TV show. But their feelings for the thieves is confusing. They have more proof that the thieves are against the Ganglers instead of cohorts. It'd make sense if the police were also trying to collect the Lupin Collection just like the thieves, but they aren't; they are perfectly happy destroying it so that it doesn't fall into the wrong hands. Only Noel cares, but that's because he's a double agent, and he hardly counts since he wasn't even there for the first half of the show.
