And this applies to the whole justice system, regardless if it's a criminal or civil issue.
In civil cases this is used as leverage by wealthy people. The wealthy can sustain a legal battle for as long as they want. They know that if their opponent isn't as wealthy, they'll be forced to settle, even for an unreasonable amount, just because they won't be able to afford defending themselves properly.
For reference, a decent civil attorney in a major city in California will charge $250-500/hour, which ends up being around $5k/month to defend pretty much any civil lawsuit. A lawsuit that goes to trial will take 18-24 months, so you'll end up paying $90-120k just in legal fees. There will also be $10-20k in additional court fees and other expenses, not to mention your time.
At the end of the day, if you defend a civil lawsuit and you flawlessly "win" the case, after about 2 years of manufactured stress, you'll be down $100-150k.
That's what it costs to prove you are innocent and walk away "free" (free to be sued again).
Btw, in civil cases, if you cannot afford a lawyer, the system won't appoint one for you, you will have to defend yourself (which judges and lawyers hate, and will very much play against you in court).
Also, even if you can represent yourself, the court fees won't necessarily be waived ($2-3k), and you'll have to fund your own discovery (which can be insanely expensive, depending on the case).
Then if you are defending as a corporation (llc, c corp, etc), you must have a lawyer. So basically if someone knows that your company cannot afford to hire a lawyer, they can sue you and force you to pay up or go bankrupt - then during bankruptcy they can keep going after you personally, and even after bankruptcy they can sue you again.