Michelle Obama has done an incredible service across the USA and the world for school children's lunch menus, children's fitness, young girls rights, etc.
She could not possibly do that without staffers.
She has to attend and speak at many state functions around the world.
A lot of your comparisons are to the 1950's June Cleaver view of women who stay at home and be exclusive home keepers to the husband and children.
After the Obama's leave office, Michelle will continue her charitable work and raise private money from grateful donors.
$2M a year seems like a great value compared to a lot of the other wasteful gov't programs in the USA.
Even in Canada, the new Prime Minister's wife, Sophie Trudeau, had to ask for and rec'd extra money and staffers to keep up with the demanding global lifestyle of a spouse to a world leader.