I'm a full-stack engineer that started out on the front end. I don't think frontend is easier - in terms of the amount of background you need to know to produce something useful, being a frontend engineer is significantly harder than being a backend one. However, frontend stuff demoes better. If you do a fancy machine-learning analysis of some public data set but present it as a command-line app or a table on some bare-bones website, people will be like "Uh, what's the deal?" If you make things fly around the screen in cool patterns, they'll be like "Woah! I didn't know you could do that!"

A lot of this is also because a frontend engineer's job is to lower the cognitive processing a user has to do, while a backend engineer's job is to come up with useful things to cognitively process. In other words, when a backend engineer comes up with a demo, they make the viewer work to understand it, while when a frontend engineer does the same they make the viewer go "Ooh! Aah!"