Are commercial DVD audio levels set differently?

I've noticed with commercial DVDs and CDs that the audio levels appear to be set high.
Some CDs I import into FCP are right at the digital 0db with no dynamic range at all.
Usual output for broadcast is to set digital audio levels around -20db with peaks at -10 or -12dbs.
depending on the broadcasters requirements.

Setting my sequence at -12dbs for prep to compressor/DVDSP, out of curiosity I popped in a DVD movie,
leaving my speaker volume untouched. The commercial DVD volume is significantly louder, which leads me to presume that since there's 18dbs of dynamic range, ( if movie's audio levels for the theatre are set at -18dbs), and no broadcast analog crossover to worry about, the DVD masters are bumped much closer to 0dbs.

I presume this is because the engineers are trying to allow for all the different types of speakers people will listen to the DVD audio on? Laptops and cheap computer speakers don't have much volume capability.

Any thoughts?