Take a look at the number of ads you'll see for personal injury lawyers in the United States. Unfortunately it's a huge, thriving industry. I believe the "sue-happiness" is a symptom of the overall legal landscape and public mindset rather than a consequence of high medical costs.
It seems the general idea in the US is that people are assumed to be idiots, so the burden is on companies to disclaim negligence or liability over accidents that might conceivably be unforeseen (by an idiot). Unless some kind of warning is placed on the cart itself (pointing out that it could tip over), it's not a stretch to think Home Depot might be found liable for a child hurting themselves in this situation[1]. All the carts in normal grocery stores are covered in similar warning signs.
Of course, some other countries tend to place a lot more confidence in the public's level of intelligence (and that's generally a good thing), but it can also be taken too far. The optimal legal landscape would probably use something in the middle of the "bubble-wrap everything" approach and the "jump at your own risk" approach.
[1] To answer your question "Would you personally sue them in such a case?": The answer is almost always "no". But those few rare cases where someone does sue can be incredibly costly for everyone involved. The only winners are the personal injury lawyers who often make money either way.
META: I know HN discourages commenting on voting, but there seems to be some odd downvote behavior going on that I haven't seen here before. I really can't imagine why this comment would get downvoted so much. To get this number of downvotes (let alone any votes this deep in a thread) in a short time smells of abusive behavior. I don't care about the points per se; it just makes me less inclined to contribute to discussions on HN when this stuff happens.