There are a plethora or reasons why people prefer sew-ins vs installs with hair glue or vice versa. Hair glue installs are faster as a quick weave can be installed in under an hour, while a sew-in would take a bit longer. However, although hair glue installs are faster, they are not as long lasting.
Hair glue is made from latex. So, with many people suffering from latex allergies, hair glue installs are not an option. Hair glue also has a smell which some may find unpleasant. If you sweat in your scalp, you many not want to use this option because when the glue mixes with sweat, it can itch like crazy and become a sticky messy substance which transfers onto the skin and can increase skin irritation with each additional scalp sweating episode. Having said all that, if you need a quick style for an event and you have only around 30-45 minutes of time to dedicate to a new hairstyle, quick weaves (hair glued) are a good option.
On the other hand, if you need a style from human hair weave which will last for a much longer time without the risk of scalp irritation, then a sew-in is a much better alternative. Sew-ins can last for months and hair and scalp underneath the sew in can be shampooed and conditioned while the hair extensions are still intact on the head. This significantly extends the life of the hairstyle when compared to glued-in styles as conditioner loosens the latex bond which causes the extensions to fall out, shortening the life span of the bonded hairstyle. Even if you are making a wig, it is better to use the sew-in method, as you will get more life out of the human hair tracks you used to make the wig.
When shampooing and conditioning human hair weave, it is always recommended to use a shampoo which is not drying or harsh. A mild shampoo or a sulphate free shampoo is usually recommended. A deep moisturizing conditioner is best in order to hydrate the hair. When styling with heat appliances, you should always use a heat protectant spray before applying any heat to the hair. Or a light silicone shield or Hair Glosser product, which will add sheen and life to the hair.
At bedtime, you should always wear a satin cap or satin scarf which fully covers the head. Cotton dries the hair out so it is always best to use a satin head covering. If the hair is straight, wrapping it before applying the scarf or cap is recommended. If it is a body wave or natural wave texture, twisting the hair in large twists and clipping the ends upward is best before applying head covering. If the weave is a kinky curly weave, jerry curl or water wave texture, large three strand braids with the ends tucked in upward are excellent protection for the hair when placed under a satin head covering before going to bed.
With a sew-in, the hair is more secure when prepping it for bed. With bonded hair, the constant tension may cause the weft to lift eventually, especially if you tend to sweat in your scalp. All in all, the longevity of a human hair weave sewn in will far exceed the longevity of hair bonded with latex adhesives. Sew-ins also allow your scalp to breathe thereby significantly reducing major scalp issues.