Other countries don't have the same notion of what good service is, and don't expect the server to be up your ass about drink refills every 30s to count as good service. They expect you to ask if you need something, so they're not bugging you. It's just a difference in what's considered better. You see the other style at finer (expensive) restaurants in the US, sometimes. It's really nice to be able to chat with your fellow diners without some stranger constantly bugging you while being pretend-nice.

I agree that service is generally better in North America (vs the UK, at least), but I'm not convinced that the tipping culture has much of an impact. Tipping is so customary in the US that I find most people just tip the same amount - give or take 5% - even if the service was terrible.