And with that slower release, blockers are able to key quicker on the set, figuring out if it's a 1, 3, 5, shoot, etc. Here's a rough diagram - noting that this all varies based on system and even from team to team:
EIL5: slower set speed = more time for the block to understand where the set is going. It may be fractions of a second, but when a hit is traveling at 80+ mph (in women's volleyball - faster in men's), those fractions of a second mean the difference between a roof block and a tool off the block out of bounds. Blocker hand/arm positioning is a split-second move, and separates good blockers from great blockers.
So you'll see the team set up for serve receive, in a cup formation with the strongest passers featured, and the setter up near the net putting up signals. She'll either face the opponent (if she's front row) or she'll be sideways to move on serve to her spot. In the seconds before the serve she's communicating to her hitters what set she's going to send them using hand signals, either behind her back...
...or off to her side. Her body will hide the signal from the opponent, and if necessary she'll pull on her jersey to block the opponent from seeing. One finger for a quick middle, two for a lob middle, three for mid-net, four for shoot, five for a back slide, six for an outside set with a high arc, either to her left- or right-side hitters. She'll make a signal to each hitter, including back-row hitters out of the pipe, so everyone knows what to expect and the play happens in the blink of an eye.
On a broken play each hitter has the skill to just go hit the ball, but on serve receive where you have your best passers feeding the ball to the setter, you're supposed to be in-system and running the play the setter calls. On a good pass, no matter the serve, that setter will get to her spot and barely move an inch before making her set, and the hitters will all know what they're getting because of the signal.
At the same time this is happening, the front row of the serving team is signalling to their back row where they're going to block, one finger for line, two for angle, a balled fist for no block, etc. That's maybe more important in two-man sand, but it comes into play on the court as well. Here, the blocker is telling the defense he'll be in the middle of the net taking out either angle shot, so the back-row defender knows to set up on a line...
... knowing this before the serve, the defender (especially in two-man sand) will serve a corner or deep middle to a specific person, knowing the pass-set-hit sequence forces (typically) the passer to be the hitter, and the server will attempt to force the set to a spot they can dig (if they're the back-court specialist) or be in position to block (if they're the bigger player with net responsibilities).