Eventually there comes a time to rest, dine, and sleep somewhere. That is the bivouac part of vol bivouac. If all goes to plan, this will generally be at the end of the day when the sun and thermals go to sleep as well. Somewhere on a mountain that allows you to take off again the next day.
If your (cunning) flight plan has not worked out the way you planned, you will probably be somewhere down in a valley such as seen on the right, preparing yourself for a (long) hike up. This might seem bad luck to the beginner, but seasoned vol bivouac pilots know they have been lucky! They profit from the occasion by having a bath in the nearby river and buying some food (if they have been lucky enough to land near a village). They also take the opportunity to sleep more comfortably than usual, since it will be less cold in the valley than up the mountain. And their luck does not stop there. They also have the chance of walking up in the cool morning air, instead of in the sweltering afternoon heat that is trapped by the same inversion that ended their flight.
Some pilots carry a tent and/or a sleeping bag. Those might not weigh that much when using ultra light (= ultra expensive) gear, but even two kilogram is just too much for me. I prefer to carry (extra) water or food, rather than something I can do without. If I would take along all that would be handy or comfortable, I would end up hauling 30 kg up the mountain (as well as flying overweight). If you have the will and the strength to do just that, then go ahead by all means. Or just read on. You might change your mind and prefer smart solutions to a show of strength.
If they would invent a spacious tent weighing only 200 g, or a sleeping bag keeping me warm down to -20 °C and weighing only 100 g, both together having a volume of less than a litre or so, I might change my mind. For now, I will do without them.
You will only need a tent to keep curious cow neighbours out (but an electric fence or wire does the same job, so try to sleep on the right side thereof as seen in the scene below), or to keep dry when it rains or the air is very humid during the night. You will not need a tent when it is (too) sunny or windy. Sun will turn your tent into an oven, unless you put it up in the shade. But if you found shade, why would you put up a tent to shield you from the sun? When it is too windy, you can usually find a lee side to shelter or build one yourself from stones, wood, brick, abandoned agricultural or military equipment, or even by stacking piles of cow dung if you are lucky (landing near or in the middle of the cow dung production facility is discouraged though). Cow dung can also be used as mortar, making your wall more stable, but this requires quite some time to dry.
In fact, you can have so much fun building your own ingenious shelter that you will completely forget about your flying obsession for a while. Possibly even never wanting to leave your new home, ever. If you are searching for a lost pilot, then do not look for a glider or a deployed parachute hanging from a tree or a cliff. Look for a small cosy shelter instead. Somewhere in a quiet place with water, food, and excellent take-off possibilities nearby. It is a well know fact that hermits living in the mountains are nearly all former paragliding pilots that have finally found (lost?) their way at age 42.
The question is: are you prepared to carry one to two kilogram of shelter when there is usually free shelter to be found on the spot? Shelter that is often more spacious and comfortable than your cramped tent (if it is not cramped, then it probably is not lightweight). If it is raining for three days, are you really going to lay in your tent for hours? For days?
Unless you brought the big spacious family tent, you will feel the urge to move about a little bit. And feel other urges as well. These urges can not be satisfied within the restrictions of your narrow coffin made out of nylon fabric. So, you will have to get out and get wet anyway. When returning wet in your tent, you will make everything inside damp or wet, which defeats the whole purpose of bringing it along. Unless you fancy a career as a sadhu, I suggest we start looking for better solutions to keep you dry.
You could plan your trip using cabanes. The only problem is that (the absence of) thermal activity or a change in the wind could very well disrupt the best of flight plans. There is a reasonable chance that you will (be forced to) land far away from a cabane. In that case, you will have to rely on your feet, or on stumbling upon (formerly) unknown cabanes or natural shelter. And if you really can not stand the challenges of surviving without excessive luxury such as heated rooms, toilets, hot meals and drinks, as well as the company of fellow travellers, there are refuges of course.