He misses far too many chances though. Iaquinta is not up to the level of DP, Trezeguet or Amauri IMO, so he HAS to take the 4th striker spot. It is what it is.
No, it is not what it is. You dislike him so that's why you say this.
Lets take a look at the numbers first:
Last year Iaquinta played 2340 minutes, scored 15 goals and made 5 assists. Amauri played 3009 minutes (669 minutes more than Iaquinta. Almost 8 full matches), scored 14 goals and made 4 assists.
This year Iaquinta played 710 minutes (4 goals, 2 assists) while Amauri played 896 minutes (4 goals, 1 assist).
During the time Amauri is here:
Amauri --3905 minutes- 18 goals, 5 assists
Iaquinta-- 3050 minutes - 19 goals, 7 assists
Amauri offers some things that Iaquinta doesn't and vice-versa too. Iaquinta hustles, fights too and he has better positioning, he knows how to run into space, how to open up. He's missing chances but he also knows how to find himself into these chances. If you take a look at the numbers above and you say that Iaquinta is missing chances, then the conclusion is that either Amauri is missing even more chances, or if that isn't true, then the conclusion is that Amauri is not finding himself in such chances. And it's true.
Look at Inzaghi. Another master of missing chances. But he still scores a lot, just like Iaquinta.
Iaquinta is also scoring a lot against the top teams. In these little more than 2 years he's in Juve, he scored goals against Inter, Milan, Roma, Chelsea, Bordeaux. In this aspect he's not inferior to the other strikers.
In CL Iaquinta scored 4 of the 11 goals Juve scored after Calciopoli. Amauri scored 1, Trez is yet to score.
Del Piero aside, Iaquinta is not inferior, overall, to the other strikers. All offer something different.
That's why he isn't a 4th choice. The choice of the striker(s) who should play should be made depending on the current form and the teams we play against. That's why on some of the matches Iaquinta will be our 1st choice striker, on some 2nd choice, 3rd choice, and yes, on some he'll be the 4th choice.