U.S. aircraft make only up to a dozen strike sorties a day. Such a modest involvement shows a lack of serious commitment by the U.S. to fighting the Taliban and helping the Afghan government.
The last thing the U.S. currently wants is an image of defeat, like that of the helicopter taking off from the roof of the Saigon embassy in 1975, on the last day of the Vietnam War.
Obama handed over the Afghan war to Donald Trump who during his 2016 election campaign had heavily critiqued the continuing U.S. presence in Afghanistan.