I made two alts to experience the other two starting city stories. Two more just for fun/goofing around with friends. Also to try out different races and genders without changing Eva (she wouldn't feel right as anything but a fem elf to me).

I enjoy leveling and questing so I tend to play the alts when I'm bored of the endgame gear grind on my main.
At the moment 3 of the alts are at the end of ARR/beginning of Heavensward while the 4th has just joined a Grand Company.
I don't plan on ever having my alts at the current expansion endgame as I don't want to feel like I need to keep up with multiple weeklies and tome capping.