All recipes call for simmering a dish if you wish to reduce. I know that if for example if I wish to reduce wine, it will take me double the time or even more if I simmer instead of just cranking the heat up to a boil. But there must be a reason for this – what is that? There is only a 6c difference between a simmer and a boil.
I also presume boiling is more permissive in some cases than others, so an ability to distinguish the importance of simmering is necessary to know when you can crank the heat up to save time.