DTS is typically about 4dB louder than Dolby Digital, which is sometimes suggested as a reason that many people prefer DTS - the ears can equate "louder" sound to "better" sound.

The reason that many discs do not include DTS is "bit budget". A DVD has a finite amount of space, and DTS typically takes more space than Dolby Digital. At one time, studios would get around this by releasing separate Dolby Digital 5.1 and DTS 5.1 discs (with a legacy DD 2.0 track on the DTS disc to satisfy the DVD standard). That practice has largely ceased, and instead we see DTS 5.1 tracks coexisting on discs with DD 5.1 tracks. The combination of those two cuts into the space left for video (potentially requiring higher compression, which incurs a possible decrease in image quality) and extra features.