Aluminium is a metal. It does not absorb any moisture and therefore it doesn’t expand. It does expand from heat, but the extremely firm corner connections make sure that you won’t notice these expansions. What’s the most important benefit? There won’t be any cracks or ruptures, not even after many years.
Aluminium is also quite strong for its weight and highly resistant to rust which gives end users a long service life, lifecycles of over 60 years are not uncommon. Despite their light weight, aluminium windows and doors are of very high quality. Their extreme stability and resistance against deformation makes aluminium the perfect choice in burglar, impact, fire, or even bullet resistance with the correct choice of glass.
One last added benefit is that aluminium is >99.9% recyclable. In fact, you can recycle aluminium almost infinitely. So old aluminium door and window profiles can be recycled over and over again hence sustainable in the long term and good for the environment.