Why do some websites not want you using a private browser?

I understand why some websites do not allow you to view the site with an ad-blocker enabled. Ads are how these sites make their revenue, so it makes sense that they require you to disable your ad-blocker before viewing the site. But how come some sites (usually news sites) don’t even let you use “incognito mode” on Chrome? I get the message “we see you’re using a private browser” and they do not allow access to the site. Why?