Why is President Biden not making the visit?
The only time in history that a U.S. president visited Taiwan was when President Eisenhower toured the country and met with former ruler Chiang Kai-shek in 1960. President Trump's phone call with President Tsai Ing-wen was the first time a U.S. president-elect had directly spoken to a Taiwanese leader since former President Carter severed diplomatic relations in 1979.
A presidential visit to Taiwan would be such a big deal that it might just prompt China to attack, or do something short of it, like freezing US assets in China or banning all electronics exports to the US.