Right now, Better Call Saul is devoting necessary time to building the narrative of Jimmy McGill and his transformation into Saul Goodman. He wants to help, but he doesn't know how. At this point, he can only be so tolerant of Chuck's eccentricities, as evidenced by his forcing Chuck to drop the space blanket. He clearly doesn't understand what his brother is going through, but he knows his brother isn't going to get better. It's obvious Jimmy cares about his brother, but that concern only goes so far.
What, exactly, is he so afraid of and how did he come to be this way? Jimmy's relationship with Chuck is an interesting one and Chuck's an interesting story. The fame and notoriety his brother Chuck had before developing his, let's call it EMF-obia, and being unable to go to work, probably sullying the McGill name in the process. Money will buy him the fame and notoriety he wants. We also know that if there's one thing Jimmy McGill wants, it's money. Jimmy insists he's no criminal, but we know that's not true based on his brother's suspicions that he's fallen back into his old habits of faking injuries to scam people as Slippin' Jimmy. Nacho offers a 10% finder's fee if Jimmy will help him steal the money the Ketelman's stole from the city. That's where Jimmy McGill's services come in. And, instead of robbing from rich people, he steals from other thieves because "they have no recourse." Except instead of helping poor people, he helps himself.
The end result of the dance with Tuco is that Jimmy meets Nacho, Tuco's second in command, and Nacho is a modern day Robin Hood. Judging by his reaction after the fact, I'm going with that dalliance in the desert being a wholly new experience, and the one by which he will become a criminal himself. It isn't quite clear if this is Jimmy's first run-in with criminals like Tuco, i.e., the kind who want to kill him and are moments away from cutting off his pinky fingers.