Being up unfortunately isn't enough. Failures are in different components (Microservices?) Today for example I was greeted by "Internal server errors" when attempting to login to my tweetdeck. A few days bay I hit a bug, where I clicked a link to a Twitter message and was redirected to my home (apparently to refresh my session as I didn't use Twitter in that. Browser for a while and second attempt worked)

Any simple "upstate" tacker won't notice those things. For me it is notable, though, while I use Twitter a lot less, which of course impacts perception.