When people generally have less income disparity, their lifestyles will be more or less the same, and over time a culture of "well we spend about the same amount so let's just split it" can arise.

In other places (like the US), some people can be very conscious about how much they're spending because it's a significant portion of their income. You wouldn't want to split the check when you had a $10 salad to save money and a tablemate had the $50 filet and 2 $10 glasses of wine.