Audio discs that are playable on DVD-V machines are CDs which are normally 16/44.1 Khz pcm & DTS encoded CDs. DVDs, now this is where it gets confusing DVDs can have a number of number of different mixes (or types) these are DD 5.1 MC mixes (@ 48khz bitstream), 16/48 PCM Stereo mixes and finally DAD a hi-resolution standard that plays 24 Bit/96 Khz Stereo mixes from companies like Chesky/Classic etc.
Now I think you are getting confused with the 2 new standards that have appeared on the market :
SACD & DVD-A :
SACD is not playable on a DVD-V player unless you get a hybrid player like the Sony NSV-900 which plays DVD-V & SACD or a totally universal player that plays all types of format like the Pioneer 747 which plays SACD, DVD-V & DVD-A.
DVD-A is a different format slightly from DVD-V in that it offers higher resolution 5.1 mixes at 24/96 and higher still 2 channel mixes @ 24/192. But as you have noted you will need a DVD-A players to access these tracks. These are not playable on normal DVD player which generally only go to 5.1 @ 24/48 & 2CH @ 24/96.
Read my review in the music section of the latest Neil Finn concert on DVD-V, this is bascially a DVD-V film and offers 2 types of mix that can be used with a DVD-V player. So you actually get DVD-V which are both films & audio discs (with video footage). DVD-A discs are audio only (no video info in time with the music) but you need a screen for selecting tracks & audio set-up.
To answer your final query the audio companies investing in DVD-A & SACd do want you to invest in another piece of equipment but what is hindering people from doing so is the severe lack/cost of software titles presently available. FWIW DVD-A is genreally regarded as a "Lame Duck" in hifi circles, SACD seems to have the marc on its rival but it is still a long/long way off knocking CD off the top perch for the general buying public.
The funny thing that the DVD-A industry seems to have missed is that many people who own DVD-V machine could access 24/96 2CH pcm mixes but they have thrown their weight behind DVD-As MC 5.1 credentials. I think once DVD-A has be shown not being taken up by the public we will once again see these types of DAD 24/96 being produced IMHO for the majority of DVD-V owners - well I hope so but I would bet on it.
HTHs
Edit :
The one point I forgot to add about the DVD-A & SACD industry is that they seem to have misjudged, is that the average hifi dude who wants higher resolution formats will take up 5.1 surround packages to listen to music, this is a big mistake IMHO.
Due to the facts of : cost, space & performance of of MC amps in stereo mode are not the best when using the current mediums of CD & Vinyl.