Design trends my friend. Parallax scrolling, large HTML5 looping video and imagery, unnecessary loading screens, horizontal scrolling and my favourite of this whole unusable design trend of late: parallax layer slideshows (where pieces fly in independently to form a slides contents).
As a developer I completely agree with you. Making a site useful versus making a site that crams as much design fodder in as possible shouldn't be a hard decision to choose between, but here we are. The theme marketplace Themeforest are BIG perpetrators of these aforementioned trends, you won't get a theme approved for sale if you don't incorporate these, "features"
