"There is a trend towards bigger screens, with the greatest shifts being towards the 5 to 5.9 inch screen size category in the United States, Canada and Australia. In the UK, the 4.5” to 4.9” was the segment to gain most in terms of share of traffic"
Presumably this is obesity driven: Bigger bottoms need bigger trousers with bigger pockets? And porkier hands will be more comfortable with larger devices even for those who don't have pockets.