Why Do Engineers Put Bolt Adhesive Inside A Glass Tube

Why do engineers put bolt adhesive inside a glass tube? It seems like a bad idea. The glass tube takes up space and the bolt cannot simply go all the way into the hole like before. So wouldn't injecting the adhesive directly be a better solution? For a long time engineers trusted this method. Workers would inject adhesive into the hole, then slowly twist the bolt inward. Once the bolt was fully inserted, the extra adhesive would squeeze out. It looked almost perfect, but the real problem was nobody could see what was happening inside the hole. Workers could not know if the bottom was completely filled. They could not see whether air was trapped inside. They could not confirm whether the resin and hardener had mixed properly. There was only this spilled glue on the spot. But this doesn't mean the entire whole wall was covered with glue. That is why engineers created these glass capsules. The biggest advantage is controlling the variables. Each hole gets a precisely measured amount of adhesive. The hole depth, diameter and bolt size are matched in advance. When the bolt is twisted into it breaks the glass tube and mixes the chemicals inside. The glass tube that originally seemed to be blocking has instead turned into the anchoring material that covers the screw. Moreover, the whole is originally one circle larger than the screw and the space filling the medicine. Which way do you trust more now?