Why the facination with integrated amps?

Just the perspective of someone who struggles with the design trade-offs, both technical and the big one **COST**.
The unsaid part here is that everything is a compromise of what we want to do, against what we can afford to do - in design, mechanical, parts quality and quantity, etc. I think the original poster, who was assailed for having a "technical" perspective was simply aware of some of these trade offs that in the end, limit sound-for-dollar. I mostly agree with them. No matter either way.

An integrated amp reduces spend on several very costly parts that don’t contribute directly (yes indirectly) to sound quality - chiefly among them one chassis vs two. The big ticket items in almost anything are the chassis, heat sinks, transformer, and trim. Electronics are fairly modest. Heck, the packaging (cardboard box, etc.) often costs more than the circuitry itself. And you cut that in half too.

So the cost can come down faster than the quality.
There are issues with integrated amps, some noted above, but what has not been noted is that with some effort and money they can be overcome. Chief among them is the power supply compromise. I’ve done a couple of integrated designs, one as a contract, and i simply did not make that compromise - easy as that. Spend the money, build multiple idealized supplies. QED.

So the theme is valid - reduce cost, hopefully with a less-than-proportional reduction in sound quality. What will be lost?:

• -- flexibility to have different power levels or to change them
• -- chassis isolation of the low level from high level circuitry (a big deal IMNSHO)
• -- flexibility to locate amps near speakers and pre-amps near the listener (another biggie to me)
• -- stuff i wont go into.

At the end of the day most people would be well served by a truly great 30W integrated. More money could be then spent on DACs/timing/speakers/vinyl reproducers where the differences are larger and the laws of physics sometimes conspire to make bigger better.

In fact I just slapped my own circuitry in a vintage integrated chassis from [fill-in high quality 1970’s Japanese manufacturer here] for my bedroom. And yep, i built three power supplies and somehow wedged them in :-)
G

The biggest downside of using an int is the lack of good heat dissipation.

Only if it's an integrated with inadequate heatsinking, as is the case with Hegels.

Desire is a tricky thought to master. Manufacturers work hard to keep us from
controlling ours. For the most part, they succeed and we all succumb in some area of life. 

I have a Naim Uniti Atom, Totem Signature Ones, my original Thorens from 30 years ago and a Parasound Halo Jc Jr phonostage. Some nice Transparent cables. It all sounds really good. Musical and eminently fun. Do you know when it doesn’t? When I go and listen to a 70,000 system at my favorite dealer. But you know what I do with the 60k difference? I invest it and average a minimum of 12% per annum. In 18 years when I retire, that will be at least 480k. So, does that 70k system sound like it is worth a half a million dollars? Not to my ears. 

And here’s  another thing. My brain can’t readily  hold on to the difference of a 10k equipment bump up after a short period of time. Like doing A/B switching. The brain adjusts. 

Moreover, if I want to hear really good music? I hang and sing with my musician friends. I don’t care what sound system you have, my friend’s Steinway will still sound better. It’s real music, not reproduced music, and it’s made with friends, so I am inside the experience. 

My relatively modest system just works and is compact. And the clean simplicity and ease of use of everything I own reduces my stress level. Lower cortisol? I might just live longer. 

So figure out what your values are, and make a decision on your stereo based on the fullness of your life and the goals you pursue. If you’ve done that successfully, the question is no longer about something as inane as integrateds vs separates. It’s about how well you are living and enjoying your life. 

Yes, you might live longer. Question is what for ?