What? Maybe you visited a particularly casino-heavy area, but in general there aren't many casinos in Spain. In many regions (e.g. mine) they're restricted to one per province. My city (250K population in the core, metropolitan area about 500K) has one. Madrid (6M metropolitan area) has four, Barcelona (5M) has one.

Sports betting places on the other hand have multiplied like fungi in the last two decades, unfortunately.