Also, most crimes aren't uncovered by lawsuits. They're uncovered by law enforcement. The reason people resort to lawsuits is because law enforcement does not rigorously investigate or monitor. Voting laws vary by state / municipality, and they're mostly run by well-meaning volunteers acting in good faith.
When we're not sure how well the TSA is doing, we try to send prohibited items through, and infamously get abysmal results [1]. IMO the reason we don't see more election fraud cases is because *we're not looking for it*, so we just see the obvious cases like when dead people vote or people brag about voting twice publicly.
Until we actually do some "red teaming" of elections, we won't ever know. But the reality is, if we actually did, the results would reduce credibility of numerous prior elections.
[1] https://abcnews.com/US/tsa-fails-tests-latest-undercover-ope...
Red teaming, yes. But also, what other signals of fraud are we able to detect? What measures of validity (or signals that sending was attempted) are there? How are they distinguishable from honest voter errors?