Unfortunately none of us can predict the future. It's those unpredictable life shattering incidents you need to think about.
For instance:
A couple of weeks ago I dislodged an ashtray that someone had left on an upstairs window sill. It was invisible from the ground but my brush knocked it off and it fell three floors and smashed on the footpath. What if someone had been walking underneath at the time? Can you be sure a court wouldn't find against you? The damages you could have to pay for that kind of accident could be in the millions.
If you're using a ladder on a public highway and you fell onto someone, the same applies.
What if you walk on a tiled roof, a tile breaks and falls onto someone?
Then there are the 'professional claimers' who would see a WFP pipe across a footpath as a gift from above - could you afford to go to court and argue that the 'trip and fall' wasn't genuine? And if it was... :

I worked for many years without PL, but a couple of incidents like those above involving near misses convinced me that I needed to protect myself from someone suing and bankrupting me.
It's the things that are not your fault that could cost you everything you own and more.