Because you don’t want to take the risk in case Excalibur is still out there somewhere.

To just piss off a small group at a time.

It's quite effective if you want to roll out unpopular things, keep the scope small and start with obvious things that most people agree with, then keep expanding using previous legislation as foundation.

Performance art.

Anything in the UK carried for the intent to harm another person is a weapon. I do lots of low impact woodland/forest work. Axes, saws etc. in my bag. If I carried them to a Birmingham park to murder someone they would be weapons and not allowed. If I carry them into a woodland I have a contract to manage, they are tools and allowed.

These extra rules/laws don't change the above. The swords could still have been outlawed as weapons by the legal system.

But... doing this means the perl clutches can sleep easy knowing "something is being done"

They are responding to crimes being committed. This helps, and minimises the scope of the law. But, it doesn’t solve root cause.