@bshep– You could save the field as a group field, with the checkbox field being the only field in the group.
OR
You can just leave it the way it is, and use get_post_meta() with the last parameter set to false. This would give you the data back as an array: get_post_meta(get_the_ID(), 'my_field', false)
Piklist saves it like this because the data is flexible. If you want to query on the data you can. Saving it as a serialized array removes the ability to query it.