They are probably thinking of attractive nuisance lawsuits. For example, if you have a pool without a fence around it and a neighbor's kid trespasses and ends up falling into the pool, you could be found liable to some degree.
A lawsuit still costs money to the defendant even if it doesn't "succeed" in the end. The legal system is pretty much inaccessible to laypeople, so you need to at least hire a lawyer so they can speak the magical incantations and file the right 27b/6 form to the right clerk at the right time so you don't lose due to a paperwork technicality.
I'm not OP and didn't make any claims about "falling down stairs and filing a lawsuit". You want me to provide a generic example of someone being sued and it not succeeding? I would guess this happens daily.
