I won't say it doesn't happen, and folks here will swear that they've encountered it, but over nearly 50 years, I've necropsied or watched necropsies on thousands of cattle of all ages, and I could count the number that had any hay twine or netwrap in their rumen on one hand and have a couple of fingers left over. I have seen wads of plastic garbage bags, and one cow had swallowed an entire rope halter... but in no instance have I ever seen a cow that died as a result of chewing and swallowing plastic twine/netwrap.
That said, I always removed netwrap, and tried my best to get all plastic twine off - it is a PITA if left out in the pasture.