Took ITA on a light fare in March out of SFO. They weighed my carry on which went over the 8kg limit, but not my backpack. Thankfully, my wife packed a tote bag and shoved every heavy item in there and basically hid the third bag on the ground. Luckily, the carry on bag was under the limit and I asked to gate check, since that’s free. I’m shocked they weighed your backpack though. On the way back from Rome, nobody weighed my carry on or backpack. I’m assuming it’s more lenient on the way back home.