There are two reasons, one ageism is one of the remaining forms of discrimination that's still socially permitted, and two some of them deserve it. I don't know if it's unsaid or forgotten but most Boomers have way more in common with Gen X, Millennials, Gen Z, Gen Alpha, and Gen Beta because it's actually a class war. It's just that the number of boomers in the wealthy classes are disproportionately larger than the other generations. Still most Boomers are not wealthy, they're just wealthier than younger people.

Also generations are bullshit. They're used by politicians and marketers to segmentize the population to make it easier to sell you on voting for them or selling you a product. The real solidarity is in class solidarity.