Because you are making more work for the teacher, who probably hates pictures just as much as you do. Since this is your first year, just let the teacher know, in the future, that you are not interested in buying pictures, and not to send them home. Or don't sign the form giving them permission to take your child's picture.
Heck, the fundraiser was probably set up by the PTO, the parents. How else would they be able to have parents preview pictures, if they didn't send them home?

If you don't like this fundraiser, join the PTO, and let them know how you feel the proper way. Leave the teacher (who will be your child's teacher

) out of it.