Why coaches call timeouts when trailing by 3 points

I noticed in the school tournament that coaches normally call the timeout when they are trailing by 3 points like 4-7 or 5-8. And these timeouts just don't seem to work in the set. There was once where my team's doubles pair was losing the second set 0-6 then my coach suddenly called timeout. So why are coaches calling timeouts at these situations? 

Hi Jasper,

This is a curious thing.  It is generally considered a position where things are becoming desperate and need for intervention.

If you notice the Chinese coaches tend to call then earlier in a match often at a crucial stage of a game when things are close.