Dubbing preferences

Is there a particular reason shows dubbed in Russian seem to always have a 1 second delay before the Russian voiceover comes on?
Are foreign audiences interested in preserving, or listening to the original dialogue of the shows? Like, this way, people can get a glimpse at the English and perhaps pick up on some of it better?

They record every basically every Dub-line separately so I would think the best method would be to lay it directly over the original line, and maybe even slightly lower the volume of the whole scene, so that the original, non removable, English dialogue isn't as distracting.

In quick conversations, obviously, some compromises are probably made, but this delay is ubiquitous.

It definitely matters more for me because I'm using the content for learning purposes, and because as an English speaker, the whole concept of watching a show that's been dubbed is........ *foreign* .

As for me: the only dubbed movies I saw were japan animes.
There is more than enough voice-translated english content for movies. All the best is translated.
But dubbed video indeed is one of the ways to learn english - it's true. I mean dubbed in english too.
Videogames still can be pain in the ass.