Mr. Lovenstein

Someone in the movie industry once told me that this is because movies are mastered for big theaters with massive speakers and THX Dolby 400.25.xqpiss MegaUltraπ+ Surround sound. Then they have to be remastered for the home when they make a DVD/Blu-ray/VHS/Laserdisc.

They used to remix it for 2-channel sound, which was totally fine, but then people started buying 5 or 7 or 11 and a half speaker setups because they wanted movie-like sound in the home for their big 17-inch black and white TVs. So movie studios had to remix it for both 2-channel and >2 channel sound. This cost money, which reduced the number of margaritas the executives could order on their Jamaican vacations, so they stopped doing that and only remixed it for people with home studio speaker setups. So if you're listening through the normal 2 speakers on a TV/monitor/phone/repurposed Ms. Pac-Man arcade cabinet, it gets compressed and all of the voices (which would normally come out of the center speaker) get split between the 2 speakers. This makes them sound very quiet relative to the car explosions. Hope that explanation makes some sense!