[eqvinox]

For PC displays on geizhals.eu, out of 3327 products:

   157 (4.7%) have  2 DP inputs
  2446 (74%)  have  1 DP input
   724 (22%)  have no DP input

Including USB-C ports,

   949 (29%)  have ≥2 DP inputs
  1806 (54%)  have  1 DP input
   572 (17%)  have no DP input

Compare HDMI:

  1350 (41%)  have ≥2 HDMI inputs
  1791 (54%)  have  1 HDMI input
   186 (5.6%) have no HDMI input

I agree it could be better but I don't think it's as bad as you make it out to be. Looking through the devices that have no DP input at all, 488 of the 572 have VGA inputs, which I'd say indicates an older generation of devices.

"Consumer" electronics (i.e. TVs) is a problem though, I'll agree.