Good point Spyro. Different tools for the job! Few speakerphiles have more than one full system mainly because of room and setup time. However, there are plenty with loads of monitors and full standers stored away. Of course there are those with ample space and a complete system in every room.
With headphones life is much easier. They are small and relatively inexpensive. The amps are also smaller and therefore one could have a rack of amps and headphones geared towards one's tastes.
Some contend that a good transducer should be able to do it all. In an ideal world, sure. But in reality, not so much. Some headphones and amps are simply better at relaying the sound of a given intrument or genre than another. Speaker fans might love to have the flexibility to hoan their speakers to a specific sound, just like vinylophiles have multiple arms and carts which excel at various music and headphone nuts likewise have various models to cater towards every form.
Again, the OP is adamant at identifying the Livewires as the be all and end all. Certainly this might be true for some, but doubtful for many, let alone all.
I like having sporty phones for outgoing activities
IEM's for laying down on my side and for those times I need isolation
Full-sized cans for better sound, multiples which cater to a specific flavour
Speakers (eventually) for the most realistic sound I can afford and enjoy with multiple people
Quite a few sets of transducers there! Not mention the handful of amps I own and of course my front-ends. By the OP's definition, I should be happy with an iPod and nothing else. It ought to be best out there with teh most flexibility right? Who needs a Dac? Or a CDP or heck...a turn table...