Presumably, cell phones have messages in their inboxes, pictures in their storage cards and phone numbers in their contacts lists. Respectively, potentially private conversations, potentially personal pictures and phone numbers that should not be given away by anyone except their owners. Therefore, it may not be wise to give someone else free access to that much personal information.
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DISCLAIMER: It should be noted that, while I strongly suspect I have Asperger's syndrome, I am not diagnosed. Nevertheless, my score on RAADS-R is 186, which makes me a pretty RAAD guy.
Sorry for this terrible joke, by the way.