I wouldn't say that is "quite common". If you throw a bunch of unenforceable clauses into an NDA/non-compete/whatever, that increases the likelihood of the whole thing being thrown out, which is not a can of worms most corporations want to open. So it is actually toeing a delicate balance most of the time, not a "let's throw everything we can into this legal agreement and see what sticks".

> If you throw a bunch of unenforceable clauses into an NDA/non-compete/whatever, that increases the likelihood of the whole thing being thrown out

I’m not sure that this is true. Any employment contract will have a partial invalidity/severability clause which will preserve the contract if individual clauses are unenforceable.

The severability clause is itself on the table for being stricken, and it's much more likely to happen if too many of the wrong parts of the contract would otherwise invoke it.