Any reason for non-continuous mountain road barrier?

I have been cycling recently in Polish mountains and when riding through one of less occupied mountain roads, I have found many places where road barrier (that is suppose to secure bikers and car drivers from falling into nearby river) is not continuous.

Some questions around:

1. Is anyone familiar of those? Can these be found in other countries?
2. Is there any particular reason for having such risky solution?
3. What am I missing in thinking that they pose a serious danger?

I was a too-close (as for me) from not stopping before one of these "separation holes" and falling into river, so I’d like to learn as much as possible about these "things".