Why not PCM audio on most Blu's

[Canada]

I know PCM takes up considerably more space than DD True HD or DTS MA. I also hear alot that companies hardly use the 50 gig's anyway, or am I misinformed. A lot of people including myself have said the notice a difference between PCM, DD True HD and DTS MA. I mean if you dont have to compromise the video quality why not put the PCM on the disk, plus another benifit any receiver can take advatage of it assuming the player/ receiver has 6 analog outputs.