There would also, presumably, be a fear of censorship targeting your entire company for over a subset of content. Back in 2018 Tumblr was blocked from Apple's app store [1] and responded by banning all adult content on the service [2] - and I'm sure there's a similar risk from school/workplace/ISP NSFW blocking services which are of course famous for over-reach.
Obviously, tumblr could have shifted everything NSFW to nsfwtumblr.com but for various reasons, a lot of sites seem to take a deniable 'turn-a-blind-eye' approach rather than visibly embracing NSFW content.
[1] https://www.theverge.com/2018/11/20/18104366/tumblr-ios-app-... [2] https://www.theverge.com/2018/12/3/18123752/tumblr-adult-con...