about the only reason is that you can elect to deduct only the cost basis of the security.
instructions from form 8283
Column (g). Do not complete this column for publicly
traded securities (PTS) held more than 12 months, unless you
elect to limit your deduction cost basis. See section
170(b)(1)(C)(iii). Keep records on cost or other basis.
capital gain property contributed is limited to 30% of AGI. this limitation does not apply if cost basis is used.
