If I sell a million dollars of stock and pay $400k in taxes, I have $600k. If I give away $1,000,000 in unrealized gains I get either nothing, or I can do a tax write off and maybe save like $200k in taxes. Either way I'll have less than the $600k I would have had. At best it's a workaround to give several other people working for the "charity" money, but at that point why not just put those people on my own payroll and give them the $600k?