Why is it a good idea? It was more a solution in search of a problem in the first place. I am no fan of minimal 2ch integrated amps in any case, just not impressive or particularly useful, especially used in tandem with yet another integrated amp in the form of the receiver. Why not just use a power amp if the amp is the issue?
In my case, I don’t want a multi-thousand dollar AVR. I watch a movie maybe once a month, and I only watch TV here and there that utilizes surround. A standard inexpensive ($500-$600) receiver is fine for what I want. An AVR is going to become obsolete in terms of features much more quickly than a basic integrated amp.
Yes, I could add a power amp to the receiver but I’m still dealing with the pre-amp it uses and all of the extra processing it does, which can actually be a pain to turn off completely (I’ve had it come back on without realizing it in the past after settings changes, updates, etc.). I sort of just enjoy the simpler experience of the integrated amp - settings changes I care about are easier and quicker to make.
Finally, I think my integrated amp on its own sounds better than sending the same source through my AVR first and then the amp.