The level of technology and civilization in Faerûn seems similar to early modern Europe just before the industrial revolution. However, there is strong magic in the setting. There are some powerful city-states who can certainly afford the services of powerful wizards, so why is the transportation system so undeveloped? It is basically limited to sailing ships on water, and long walks or slow, ox-driven carriages on muddy and unkept roads. Not that there would be no need for it, there is trade between the major cities, but it is still done the slow and tedious way (weeks spent traveling by cart).
If there is powerful enough magic to change the weather, teleport, summon matter from nothing, why is the transportation system so undeveloped? What stands in the way of making "magitech" trains, aircraft, or just hire a wizard to teleport a vehicle to the destination town?