"Other presidents, including Barack Obama, would customarily donate a percentage of their income to charity every year."

Correct.  And they did it without making a big whoop-de-do.  Here's why:

“𝗕𝗲 𝗰𝗮𝗿𝗲𝗳𝘂𝗹 𝗻𝗼𝘁 𝘁𝗼 𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲 𝘆𝗼𝘂𝗿 𝗿𝗶𝗴𝗵𝘁𝗲𝗼𝘂𝘀𝗻𝗲𝘀𝘀 𝗶𝗻 𝗳𝗿𝗼𝗻𝘁 𝗼𝗳 𝗼𝘁𝗵𝗲𝗿𝘀 𝘁𝗼 𝗯𝗲 𝘀𝗲𝗲𝗻 𝗯𝘆 𝘁𝗵𝗲𝗺. 𝗜𝗳 𝘆𝗼𝘂 𝗱𝗼, 𝘆𝗼𝘂 𝘄𝗶𝗹𝗹 𝗵𝗮𝘃𝗲 𝗻𝗼 𝗿𝗲𝘄𝗮𝗿𝗱 𝗳𝗿𝗼𝗺 𝘆𝗼𝘂𝗿 𝗙𝗮𝘁𝗵𝗲𝗿 𝗶𝗻 𝗵𝗲𝗮𝘃𝗲𝗻.  𝗦𝗼 𝘄𝗵𝗲𝗻 𝘆𝗼𝘂 𝗴𝗶𝘃𝗲 𝘁𝗼 𝘁𝗵𝗲 𝗻𝗲𝗲𝗱𝘆, 𝗱𝗼 𝗻𝗼𝘁 𝗮𝗻𝗻𝗼𝘂𝗻𝗰𝗲 𝗶𝘁 𝘄𝗶𝘁𝗵 𝘁𝗿𝘂𝗺𝗽𝗲𝘁𝘀, 𝗮𝘀 𝘁𝗵𝗲 𝗵𝘆𝗽𝗼𝗰𝗿𝗶𝘁𝗲𝘀 𝗱𝗼 𝗶𝗻 𝘁𝗵𝗲 𝘀𝘆𝗻𝗮𝗴𝗼𝗴𝘂𝗲𝘀 𝗮𝗻𝗱 𝗼𝗻 𝘁𝗵𝗲 𝘀𝘁𝗿𝗲𝗲𝘁𝘀, 𝘁𝗼 𝗯𝗲 𝗵𝗼𝗻𝗼𝗿𝗲𝗱 𝗯𝘆 𝗼𝘁𝗵𝗲𝗿𝘀. 𝗧𝗿𝘂𝗹𝘆 𝗜 𝘁𝗲𝗹𝗹 𝘆𝗼𝘂, 𝘁𝗵𝗲𝘆 𝗵𝗮𝘃𝗲 𝗿𝗲𝗰𝗲𝗶𝘃𝗲𝗱 𝘁𝗵𝗲𝗶𝗿 𝗿𝗲𝘄𝗮𝗿𝗱 𝗶𝗻 𝗳𝘂𝗹𝗹."  -- Matthew 6:1-2

Of course, it was easy to dig the information out of their 𝙩𝙖𝙭 𝙧𝙚𝙩𝙪𝙧𝙣𝙨.