Just to add a bit of balance . . . . .
Sometimes what people call a "mid-life crisis" is actually an awakening of the awareness that your life isn't what you would like it to be, coupled with the fact that you know you could make it better. (not to be confused with say, wishing you were a millionaire, or you were 20 again)
For those people that believe you only get ONE shot at life, it may be the catalyst that shows you an opportunity to move on, whether from a work or a personal situation, to something better or more fulfilling.
I guess the "crisis" bit comes from the mess these things often tend to leave behind them, broken families, debts etc, but with a bit of consideration and tact, it doesn't have to be like that.
As for people judging other people in these situations, particularly their parents, life sometimes has a funny way of working out. And it's not inconceivable that in 20 or 30 years time you may find yourself in the position your mum/dad were in when they made what you considered to be a bad decision.