So that people could...
Commute to and from work, shop and eat downtown. Right now the taxis are geared towards tourists. Given San Antonio's climate, with the proper marketing, picing and scheduling the river taxis could be a viable alternate mode of transportation to and from work downtown, for shopping and for dining (perhaps in partnership with VIA).
Because I want San Antonio to be...
Enjoyed by the citizens of San Antonio as well as the tourist.
(flickr photo by eschipul)