i think it's the by now internet-meme worthy difference between walls in the US compared to most of Europe. i've never lived somewhere which didn't have thick brick or concrete walls. 30cm was a bit high, more like 20cm.

i've seen tons of americans making holes in their walls by punching or falling into them. could never relate myself, i'd have a broken hand or concussion :D

my phone is not very powerful, maybe that's a factor.