In the US, law is an adversarial system. The DA is gonna come swinging at you with everything he's got with the expectation that your lawyer is going to do the same. The results of that fight we call justice.

The law isn't set up for 1st round knockouts. Even in slam dunk, definitely guilty cases, the law is set up expecting a defense attorney to mitigate the damage.

If the goal is for a petty thief to get 2 years in prison, the DA is gonna aim for 10 years expecting a fight or a negotiation down to about 2 years. But there's no mechanism for the DA to go easy on you because your lawyer sucks or doesn't exist. If you don't fight the charges or negotiate something you get petty crooks in jail way longer than normal. That's why we have public defenders. It's the law saying, "it's not much, but it just wouldn't even be sporting otherwise."