Many people who know nothing about receivers buy on the basis of Watts/channel and not much else. So, in order to compete, many manufactures use the "looser" spec so they don't lose business, sometimes even letting the distortion go up, because that gives you more watts.
What's important is the distortion, the W/ch at 20-20k at that distortion, and the damping factor, as well as the features you want and the sound you want.
Watts are extremely unimportant as you need to double the number of Watts for just 3dB, so the speaker choice is often more important, since speakers can have quite a variation in efficiency, as well as impedence.