User blog comment:Danz The Pure/Item upgrade paths from weakest to greatest/@comment-24706802-20140319123239

The significance of having big items is that it adds another level of strategy to the game. Rather than knowing that they can just recall at any time and have someting to buy, players have to consider the amount of gold they have in relation to what they need. Having everything build from small items would take away this aspect of the game. A common examples is some ADCs, who need to consider between the earlier back for just a Vamp Scepter, and the later back for a BF sword.