Inter Modulation Products

Why Intermodulation products of second order are not considered to be a big issue in nonlinear amplifiers?

Because 3rd orders are "in-band products" however 2nd order IM products are also important in wideband amplifiers.

Second order IM products are also in-band products; isn't it?

Lets say you have two tones in the ISM band: 2.4 and 2.41 GHz.

2nd order products will show up at 4.8 and 4.82 GHz--easily lowpass filtered.

3rd order products will show up at 2(2.4)-2.41= 4.8-2.41=2.39 GHz. ALso at 2.4-2(2.41)=2.42 ghz. Both are in-band.