Let’s get one thing out of the way: it’s not normal to stuff $100,000 in cash into a suitcase and then check said suitcase on to a domestic flight. It’s extremely weird, in fact, not something you’d expect a typical person to do in their lifetime. However, doing so is emphatically
The point is, that’s not enough. You have to prove it in a court of law. Which, for $100,000, might cost most of that $100,000 and years of time.
There have been some clear-cut seizure cases where the legitimacy of the money was obvious and it was either not worth the legal fees to clear up or simply insane to clear up. We are a “reasonable doubt” country for a reason, and if you can’t prove someone came about their money illegally, you shouldn’t be stealing it from them.