Because getting the win matters more to them than the diversity.
Via Daily Wire:
The party obsessed with racial and gender diversity is ironically headed for a rich, all-white, cisgendered male ticket in 2020. Former Vice President Joe Biden is looking to tap Democrat darling and Congressman Robert “Beto” O’Rourke as his number two on a potential 2020 run, sources told the Associated Press.
Biden, 76, is looking at O’Rourke, 46, mainly to offset his old age, the report said. If Biden were to win in 2020, he’d be the oldest man ever elected to the presidency. Ronald Reagan was elected at 73, holding the current record.
The hypothetical ticket would have precisely zero intersectionality points — which are critical to the left. Biden and O’Rourke are both white, male, heterosexual, “cisgender” and wealthy.