Not only of D, plenty of GC enabled languages (including .NET based ones) provide such capabilities, but for some reason many learn wrongly that having a GC means 100% heap usage with GC only allocations.

I think most of it comes down to not knowing how a GC works internally.

I think it is a mixture.

Your remark, additionally being taught programming on languages that indeed use the GC heap allocations for everything, and on those that allow fine grained control over resources it is usually left for "exercise to the reader", so many don't care and so aren't aware of what they are losing.