Nope; it is. Manufacturers of amplifiers assume that you always want to drive them to full power (even though in real life you have to scale the power back for a high duty cycle to keep from frying most of them) and so set the minimum input power so that one can do that without exceeding the FCC gain limit (or, in many cases, even getting too close to it). Let's put it another way. Suppose I want 300W of output power and buy a 600W amp so that I can work digital modes at half the maximum (as is recommended by virtually all manufacturers). Many such amps will require 20W or more of input power from the exciting transmitter to avoid exceeding 15dB of gain (roughly a factor of 30). So, a QRP transmitter won't excite the amp, even if it has automatic level control (ALC).