The 5th Element is best described as a tongue-in-cheek, pulp sci-fi comic taken to film format. Which is why it's so great.
But here's the thing about speeders: in Star Wars, it makes sense for them to be around - Luke's civilian model is made for offroading. No suspension, no getting stuck in the sand. Likewise, we see the exact purpose of the rebel speederbikes in Return Of The Jedi - again, personal offroading vehicles for going REAL fast in places where conventional vehicles can't. You also have to take into account that in the super-high-tech world of Star Wars, the technology for speeders and speederbikes is relatively cheap and plentiful.
On the other hand, what would be the point of the (probable) massive expense in producing non-AV ground vehicles that *float*, particularly for city use? Sure, the potholes on RED probably get pretty bad but I somehow doubt manufacturers of high-tech vector-thrust vehicles take the road conditions among the poor, hungry and downtrodden into account when designing their next product.