I think it depends on what you and your players enjoy during a game.
If your players are averse to that sort of "role-playing" and would rather just get in there, then maybe you should discuss more with your players about the kinds of encounters that you enjoy in a campaign.
Hopefully, you can meet some middle-ground that is suitable for both you and your players.
From a player point of view, often times we try seize every advantage we can, especially if it is from the BBEG. If the BBEG opens himself up to attack by "wasting time talking", an opportunity is created.
In addition, for myself, it has always bugged me when I watch a show or movie where there is an unrealstic amount of time spent by the BBEG "ranting" or leaving the hero in a "death-trap".
For example, the scene in Austin Powers where Dr. Evil leaves Austin and the girl to be devoured by man-eating porpoises. It is a parody of all the times the villains could have killed the good guy and be done with it, but instead, leave them in situations where there is always a chance for escape. In a movie like Austin Powers, it works, since it is a comedy.
But if it is a movie, or even a DND encounter, that is trying to be played "seriously", the suspension of disbelief is hard to maintain.
As a player, if the BBEG is spending time "ranting", it would be hard to maintain that suspension of disbelief if the PCs just stood around while the BBEG gave its rant.
Not that BBEG ranting is a bad thing, I quite enjoy them, but the whole "realism" aspect is not there. I realize that "realism" is relative to the type of campaign you play in, but in my opinion, there must be some sense of "realism" to go hand-in-hand with "suspension of disbelief". Realism defined, perhaps as using "common sense".
To take a line from the movie "The Good, The Bad, and The Ugly"
"When it's time to shoot, shoot don't talk"