Why does the bulb have a glass around the inner structure where the filament and other things are placed?

so The hot filament is protected from oxidation with a glass bulb that is filled with inert gas (or evacuated). In a halogen lamp , filament evaporation is prevented by a chemical process that redeposits metal vapor onto the filament, extending its life. The light bulb is supplied with electrical current by feed-through terminals or wires embedded in the glass. Most bulbs are used in a socket which provides mechanical support and electrical connections.