Workplaces often run drives for well-known established charities like United Way, and getting good participation makes employers look better, they think. Joe Davidson of the Washington Post has a story on the Combined Federal Campaign, which has seen possibly less money donated but more time.
I can remember being pressured about the United Way donation once in the 1980s when it hadn’t been done. Once I was pressured, in the 1990s, about blood drives in a way that was insensitive and inappropriate.
Some employers have tried to get associates to volunteer to causes that they deem expressive of the company. This has happened with some Wall Street firms, who can be aggressive in wanting to look good in terms of "karma".
I’m retired, so this can’t affect me now, but autonomy in my own decisions about these matters is very important to me. I think that some of the "Give Direct" operations may deserve more attention i the future.