#1) You no longer have to stand up, pull back the bow which creates movement that risks spooking the turkey or deer.
#2) Hunters can't hold back the draw on a bow forever like you can with a crossbow.
#3) The accuracy and range of a crossbow is much greater and requires so much less skill than a traditional bow and arrow.
Outside of those few weeks anyone can hunt with a crossbow, if you are handicapped and fill out the proper permits, you can hunt with a crossbow during all of the archery season. There are good online crossbow hunting videos that will help you with gaming laws. Getting qualified for this is usually having your doctor fill out a form that classifies you as permanently disabled. Now they aren't easy to come by because that same form can be used for you to go and collect disability money from the Government, so it's not as simply as just lying to the doctor. Crossbow hunting in Illinois is another option as well.