Bivies make absolutely no sense to me. An ultralite tent weighs 740 grams. An ultralight bivy weighs 510 grams. The tent takes slightly longer to setup and tear down and is a bit bulkier, but not much. Why would anyone not be willing to pay 70 grams for all that a real tent gives you?
What’s the biggest advantage of a tent? Less condensation. Bivies are notoriously bad at keeping you actually warm because of all the condensation build up in contact with your bag. This is why all those nights I slept directly under the stars in my 3-season bag on those moist, sandy Salmon river pulls never gave me any problems. Hell, it even rained on me a few times but I stayed completely warm. The moisture would immediately evaporate. That does not happen with a bivy. If you have never been in a tent and felt the walls of the tent the next morning after a chilly night in a high-humidity area you don’t know what this is like.
Perhaps some are too scared of the critters and crawlers around them and the bivy makes them feel safe. But that bivy ain’t protecting your from anything that a well zipped-up sleeping bag would. Just get an insect net for your face if bugs bother you. That rattlesnake cozing up to you for your body heat can bite right through that bivy, buddy (or your tent for that matter). But that never happens. A rattler has to feel really threatened to bite and the older ones know to hold their venom for prey that matters.
And bears? Well, do I even need to mention it? In fact, having stuff between me and those creatures is even more scary. I can’t mace a bear through the bivy or the tent wall, but I can from my bag. I’m also ready to make a hasty retreat better after pissing off the bear with that mace (or human, as the case may be).
That’s right, I’m saying it is safer to sleep without a tent or a bivy because you can be much more aware of what’s around you and react more quickly to threats that come your way. Just watch any war or western where they draw their guns immediately when approached. It’s not fiction.
My MSR tent even comes with an option to just setup the shelter with a tarp without the tent itself. This is critical for providing sun-shade during the day out in the west. And is absolutely ideal for low-insect areas where you just need shelter from potential rainfall that night, which isn’t very often really. In such cases the tent is just a tarp with guaranteed support beams. Most nights I’ll just be sleeping on my RidgeRest directly. And for those few nights that more is needed, well, if a tent can’t cover it then a local lodge will.
And forget about working out of your bivy. Most bivy people don’t consider that, but, again, why not pay just 70 grams for the option?
Bivies are just stupid. In fact, most people who use them aren’t really outdoor people at all. Usually, they are pro-cyclists who got into bikepacking without any real outdoor skills training or experience. I don’t care how many records they are breaking, they could have broken them with a tent instead (and been faster and more comfortable). Besides, these burn-through-the-night people are blowing the best part of the entire thing. Sure “it’s not a tour” but why take all the risks and hit to your emotional health cycling all those hours on remote trails with no light but that from your lights powered by heavy batteries (no Dynamo covers enough for night riding any amount of time). Here’s an idea: save on that extra battery you didn’t need and buy yourself an actual tent with the 300 gram savings in weight from reducing that battery size.