The answer is because there is a fledgling industry dying to jump into the void created when the HiFi world moved away from analogue into computer-based digital systems rather than CD -based systems which everyone knew sounded different.
Hide-bound conservatism is part of it, but it is also in the nature of what many see as a part and parcel of the hobby, the need to tinker. Any hobby requires and action by its followers, but HiFi is a curiously passive one. After you have accumulated the components, what next? you could sit back and listed to the music, but then the music is the hobby, not the HiFi, so the net result of a hobby which can satisfy far too early in the piece is to add bits, change bits, play with the peripherals, try everything out in the endless quest of a perfection that probably does not exist, but preserves the hobby as a hobby and not just as a tool for music appreciation.
A model train enthusiast does not stop once he or she has a couple of locomotives, some rolling stack and a track. There is an endless array of things to add and change. Similarly a stamp collector doesn't stop having collected stamps from one country, their are rarities, misprints, and stamps that are the envy of every other collector. With HiFi, once you have good speakers, good amplifiers and good sources you can stop and concentrate on what the HiFi does, produce convincing sounding music. However, in an analogue system you can continue with the tinkering side to important to many hobbies by changing cartridges, arms, turntables etc. The need to continue was recognised by the astute in the late seventies hence the growth of the peripheral industry, with accessories of dubious worth such as different interconnects, speaker cables, stands and even fuses.
The CD was the first digital source, and was thanks to Philips and Sony in agreeing to sell their transports to hundreds of manufacturers that digital was initially seen as just another source, less flexible than the turntable in terms of tweaking, but nevertheless allowing upgrades that always sounded different. Besides, interconnects could change the sound of a CD player, plus you could add attenuators (sometimes really necessary, given output voltage fluctuations), have them reclocked, continue with the hifi hobby.
Unfortunately, streaming, computers, network players, separate DACs etc breal the mould. Once you connect a computer to a DAC, assuming you have a bit perfect output, that's about it. Digital cables, especially if you use S/PDIF, are essentially all equal. One DAC in terms of the conversion is the same as another. Issues such as jitter, which has been around since the CD, is no longer a problem. The sad truth is a file on a computer is sent to a DAC by a digital system that effectively cannot by tweaked, unless you apply filters at the software level to modify the sound, which goes against the fundamental principles of HiFi.
However, a hobby cannot just stop. Jigsaws are interesting when you assemble them, but afterwards, what do you do? They're unsatisfying unless you buy another. so it is with the HiFi hobby. The fledgeling industry says you can continue, not only with the analogue side but also with the digital. So, hard drives sound different, SATA cables sound different, you need physically and electrically silent power supplies and so on; in otherwise, the hobby can grow into a whole new area. Forget the objectivists, they kill a couple of the most important parts of the hobby, the need to change, the need to tinker. Once you accept that digital is another analog, and you can take an SSD drive home to try on a 30 day return basis, once you accept that it is your ears that count, then you can relax and have a nice glass of whisky. The hobby isn't dead, after all.
I sometimes wonder if it wouldn't be better to accept that we need to believe the lie for the hobby to continue. Then I think what the f*ck and put a record on.
