for me I can use my work computer and log on and read on a larger screen. Or perhaps type Emails, Calendar Events, Reminders easier on a larger keypad than the iPhone. Also, for some odd reason, my iphone takes longer to view new mail at my parents than using their computer. Their internet connection and WiFi are kinda slow.
I use iCloud all the time while at work as well. My @icloud.com email is my primary personal email address, so if I'm going to write an email longer than a few sentences, I'd much rather do it with a real keyboard and monitor (than on my tiny 3.5" iPhone screen). I'm actually writing a lengthy email to someone right now via iCloud.com.