I suppose, to minimize its use. If annotations have the same syntactic weight as normal statements, such as “if” or “for” statements, there’s a temptation to us

I suppose, to minimize its use. If annotations have the same syntactic weight as normal statements, such as “if” or “for” statements, there’s a temptation to use them liberally, which is clearly not a good fit for Go. By making them comments, Go subtly signals that these are exceptional, making them less prominent and harder to abuse.