Because Bon Jovi is astoundingly good, by now, at being Bon Jovi in front of an arena full of adoring fans. They know which singles to play when (a little "You Give Love a Bad Name" to whet the appetite, then some new stuff, then "It's My Life"); they know which rock poses they need to be making at any given moment (keyboardist David Bryan has rescued the face-the-crowd, keyboard-on-either-side strut from '80s music videos.)
And they know that their fans, for the most part, will go just as crazy for a five-year-old country-crossover hit ("You Can't Go Home," sans Sugarland, sat in the middle of the encore) as they will any talkbox-heavy '80s hit this side of "Livin' on a Prayer."
They're a nostalgia act, but unlike any of their contemporaries, they've shown a knack for making people nostalgic for their new material. They've grown with their audience -- from sinister-sounding riffs and Springsteen-y New Jersey angst to optimistic paeans to loving this town and doing things Because You Can -- in a way that seems cynical from a distance but probably isn't.
Your mom is Bon Jovi's age; they both loved angry metal when they were young and developed a taste for twangy acoustic guitar later on. It would be more cynical to not change anything.