Low spoke count wheels are currently fashionable on the basis that they are more aerodynamic. In the past, light weight was fashionable, and higher spoke counts allowed a lighter rim and overall wheel weight.
My personal feeling is that low spoke counts matter most for high-level competition, or those who aspire to such. For everyday riding, a 32 or 36 spoke wheel is perfectly fine and much more durable and affordable than a high-end low spoke count wheel.