It's not just that. Yeah, the 3rd row becomes the 1st and on paper you "only lose" the back couple rows. In reality, you've just changed the sightlines for every seat in the lower bowl along the sides - some to the point that the view of play along the near side is now obscured to some degree. That damages the value of those seats. The upper bowl is also affected, but not as badly - but that's not where the big dollars are for seats.
Not to mention, existing infrastructure in arenas that covers the ice surface creation and maintenance would have to be revamped to handle any extra width. That isn't cheap either.
The "rip a few rows out, make the ice wider" idea sounds so simple, though - and it is, and it's easy to imagine all the oft-touted benefits. When you run into reality, though, the obstacles are huge and the benefits are nearly nil [other than probably reducing hitting]. This idea has been mentioned several times in the past, and I have yet to see anyone come up with even a semi-feasible solution to the sightline issue that would be cheaper than building a new arena.
And no, there will not be a rash of new arenas getting built solely for this.