Back in the day, safari 2.0.4 encountered a large amount of site breakage because sites were using useragent.indexof(“4”)!=-1 as the test for “are you Netscape 4”, and if you were then they’d use netscape’s layer apis (netscape’s alternative to css). Any changes to the user agent are very scary - that’s kind of how they ended being as terrible as they are.

Yet still sites continue to use the user agent to gate access. The same sites also like to complain about how bizarre UA strings are.