When I was called for jury duty there was a PT college student there who wanted to be excused. The judge offered to delay her service until summer. The student who had just been urgently protesting that she couldn't
possibly miss class changed her mind and decided to stay on. When asked by the judge what had changed that she was suddenly able to miss classes, she quite honestly answered that she'd rather miss her classes now than any of her summer break later.
Another complained about missing work....the judge asked when their vacation was scheduled for the year...he would reassign them to the jury pool that time. Guess who else opted to stayed on?
Judges hear this dribble day in and day out. I'd say 75% of the people called tried to get excused, maybe 10% actually were excused or delayed.
In most cases a delay in serving is all that is required, few people should be excused outright. I also understand that it's not set up to work that way in a lot of areas...you either serve now or are excused until the next time your name is pulled.