Given all the unsavoury things that kids can get up to these days, I'd have thought the last thing society would want to do is blight bits of architectural concrete with 'skateboard prevention brackets'.
Of course, we could always ban skateboarding completely, and while we're at it wrap <18 year olds up in bubble wrap (cotton wool being so 1970). If we did that, we also wouldn't need advice like this .
Note: This post was updated on 2020-11-30 to fix broken links