Question about San Antonio

[Jeeper]

Forgive me if this has been answered before, but I'm curious why San Antonio doesn't have more highrises than it currently does. The city's population would seem to support them, and the River Walk would appear to be a magnet for commercial and residential towers. I'm just kind of surprised that SA's tallest is a hotel, and that a city of SA's stature doesn't have something more substantial.