Diesel does have it's advantages in certain applications. Properly maintained, it will outlast the machine it is mounted on. It also develops tremendous torque and has very low fuel consumption.
The downsides for lawn and garden equipment are weight, cost and noise. BCS is already expensive enough without the added cost of a diesel and would be an absolute brute to handle. I doubt if many would be happy with one on a snow blower, cold starting and weight would be issues and really, why bother when gasoline engines work so well. Diesels work best in a constant speed and load environment.