Of course the ultimate in integrated music systems is the self amplified connected loudspeaker–an all in one pair of boxes with amplifier, DAC, volume control, and speakers. Yet, few speaker designers tread in these waters.
When you design a traditional loudspeaker you use passive crossover components to separate frequencies and direct them to the proper driver: highs to the tweeter, lows to the woofer. You trust the user will attach a proper power amplifier, but once out into the world, there's little control over how speakers are connected.
Far more control can be exerted by the speaker designer if the speaker's self amplified. In an active design engineers tailor the amplifier and crossover to the drivers for best performance. Even more control benefits are had when the designer also controls what goes into the self-amplified speaker: the DAC, volume control and power supplies.
Despite these benefits very few integrated speaker systems can be found, though there have been a few brave attempts in the past.
I think the lack of integrated speakers systems is a function of price, category and customer. In lower end audio systems there are numerous integrated speakers because customers appreciate convenience and simplicity.
In the high end world, where performance seems coveted over any other attribute, you'd think the improvements possible with an integrated approach would be a thing of value, yet, the opposite seems true.
Most Audiophiles I know want the freedom to mix and match for best sound. And it is this desire for customization that seems to doom the ultimate integrated approach.
Or perhaps, it might be that no one has yet done it right–so well that there can be no other choice.