Consider, nobody says you need an electron microscope to get serious about photography, but they can take some amazing photos even without using photons...
Even professional photographers that only do a specific kind of photography professional nearly always have amateur interests in other photographic subjects that require different gear.
I have even known someone to go the other way and sell off there kit for a point and shoot. They where into candid photos so always having a camera was more important than fiddling with a massive beast.
Granted, camera's are cheap to most of the HN crowd, even blowing 30k over 20 years is just not a big deal. But, just because gear is 'cheap' and 'better' does not make it necessary.
A single lens camera is as limiting as only owning one size of screwdriver, or one knife.