Is knife crime really on the increase, or is it merely being given a higher profile by the press?

I think it is both. Sure, the press are more focussed on it at the moment so any items will get reported more prominently. However, this is something that feeds on itself. Press reports are likely to cause people to go armed - both as copycat and in a mistaken idea that they should protect themselves. Others will go armed with a knife, maybe with no intention of using it, to show they are hard and part of the street culture.
Unfortunately, I don't think Police statistics on knife crime are of much help here as we know that reported crime is only the tip of the iceberg.

Knife crime in Scotland during the 1970's was as prolific, if not more so than it is today. Culture tends to ebb & flow into a gang mentality, changing their choice of weapons.

Although recent events have been *highlighted* by the media. Knife crime is a serious issue that needs to retain attention for necessary precautions to be taken by the public.