Its not a necessity, however, it would be recommended. If its done right, everything should be about the same when it goes back together. On older toyotas that have the adjustable lower control arms, when we replace ball joints we usually do the whole arm and new cam bolts and hardware for the lowers as well. They tend to get rusty and stuck so its worth the investment on older vehicles to just do it all at once. So it just depends on the condition of your vehicle and how much you wanna put in it. If its newer and you can get the ball joints out without taking a bunch of other stuff loose with it, youll probably be fine without an alignment if its been done recently.