Necessary according to who?
Both of these things are mis-handled by many companies, who will use it to encourage more performance out of those who are already as productive as practically possible, and that the tools are used in bad faith or with no intention of helping people, only as an excuse to fire them.
It’s the same with software. Your direct manager should know if their employee is in the bottom 10%. If they don’t, they aren’t doing their job or they have too many reports.
What constant automated monitoring allows is cutting back on the number of managers and like you said, pushing high performers even further.
You're right that this doesn't need to be constant or even that automated though.