That is what they do to an extent though.
In the standard World Cup, the top 25 of the World Cup are entered plus five best performers from that weekend not previously qualified to allow for form.
At the Worlds and Olympics, the qualification if I remember rightly goes (in order of priority):
- All individual medal winners from the championships to that point (the mass start is invariably last save maybe the relay)
- The top 15 of the overall World Cup, if not already qualified under 1)
- The best performers at the championships not already qualified under 1) or 2).
In theory therefore, there would be a minimum of 6 positions available on form at the Olympics, if the sprint, pursuit and individual had 9 different medalists, none of whom were in the top 15 of the World Cup, but obviously that's somewhat unlikely. In fact, I believe Denise Herrmann and Tiril Eckhoff are the only medalists in any individual discipline who isn't in the top 15 of the World Cup, so there's 13 women and 15 men who are entered in the Mass Start based on their championship performance (and obviously if medalists didn't get an automatic invite so there were 15 women also, then having won and podiumed respectively, Denise and Tiril would obviously have qualified as one of the 15 best championship performers outside the top 15).
It will also pass down the line if people elect to DNS, we can be fairly confident that Tandrevold will not be taking the start at the weekend, so her invite will pass down the line to whoever is next on this week's performances. Others may arise, but she's the only obvious case at the moment.