Yeah, but before when you didn't research Bridge Building (I think that bridges now come with Construction), you couldn't build bridges on the river tile, making a two turn loss of movement for a one-move unit. In Civ 2, they tried (and failed) to make up with this by making rivers give movement like roads, but that move didn't work very well since people wanted to move across the river instead of along it, and people correctly pointed out it wasn't logical; if anything they should be losing movement points. Then when you got Bridge Building, you then had to get your settlers all the way back to the rivers and start building roads all along the rivers' length (very slow and tedious). The Civ 3 way of putting the rivers along the edges of the tile is much better, and I hope they never put them back in the middle again.