At least in my case, it's not so much a matter of disliking bivy sacks as it is that there are now better choices. When there were no solo tents, and two-person tents weighed 6 or 7 pounds and were stuffy in hot weather, a one pound silnylon tarp and one pound bivy was a great option for saving weight. As soon as three-pound solo tents with lots of mesh became available, the tarp and bivy became a second-best choice - and now we have pound and a half or two pound tents. They aren't any better or worse than they ever were - they just got bypassed.