Cable Television, as we perceive it today, is in a steady decline (I'd cite something; but even the most cursory Google search will turn up dozens of articles confirming). While I recognize your concern about the cable company ownership and DRM, I believe that over-the-top services like Sling or DirecTV Now in conjunction with Netflix and Amazon are far bigger threat to Tivo and the like than anything the cable companies themselves can do.
You're inferring that they're related, but I see them as orthogonal.
I'll take your word that it's poorly implemented. From my POV it just works—my two experiences are with a TiVo and an HDHomeRun (first with Media Center, now with Plex's beta DVR feature), and in both cases use has been uneventful.
That people don't know it exists doesn't surprise me, since the cable industry has always fought this FCC-required concession to consumer choice. If anything, it strikes me that cable was highly motivated to ensure CableCard's failure.
I don't have any love for CableCard, but I'll be sad when it goes because it'll mean that kind of interop is gone forever.
And that makes it the biggest threat to Netflix when net neutrality (and particularly the specific prohibition on ISPs favoring their own video services) is killed by the new leadership at the FCC.
I recall someone saying that technicians would bring a basket of CableCards and hope one of them would work.
Mostly though cable crypto is dominated by two companies who provide the head end equipment and who for a long time provided all the settop boxes - they didn't want to lose that lockin so while they were mandated to provide cable cards they weren't all that happy about it
Today, the best audio drivers are external USB DACs and amplifiers. You can extend your storage with GB of USB flash storage. USB->Serial has kept up as a legacy option (although its latency issues and Win7 transition has made things difficult to work with in practice... gotta keep that old WinXP box to work with a lot of Serial stuff. But that's not USB's fault per se and more about Windows Vista's new security model).
Audio (DAC, Headphones, Synthesizers, USB->MIDI, Instruments), Storage (USB Flash Drives, USB Hard Drives), video game peripherals (XBox Controllers, PS4 Controllers, Joysticks, Driving Wheels), even legacy (USB->Serial Modems if you really need it) are all supported from the 5Gbps USB3.0 port.
PCMCIA was needed in the 90s because computing power wasn't good enough. DMA transfers, directly to the computer's RAM, was the only way to get latency / bandwidth requirements of practical devices.
Furthermore, hardware interfaces were obscure. Your "Jazz drive" external storage was SCSI based and required a specific device. USB internet modems were years away from being invented (and thus you used PCMCIA modems on those laptops).
In essence... PCMCIA was the way you attached external devices to laptops back then. More so than USB or Firewire. Modern interfaces are more secure, more inter-operable, and faster.
I mean, those flash-sticks require a rather beefy CPU to handle all of the USB-packets that go back and forth between the OS and the USB stick. That level of miniature processor power just didn't exist in the 90s, so "dumb" hardware attachments had to use simple direct-to-memory transfers through a relatively simple bus. I wouldn't be surprised if a modern USB-stick's processor had more computing power than 90s-era laptops.
Data transfers are handled in hardware; the MCU in these is not really powerful. Many are just 8051s. USB 3.0 controllers are a bit beefier, though.
For storage expansion this was easy way to get more space but of course network cards required additional dongle for the RJ45 connector etc. But still the idea was awesome :)