Open Education provides a way for teachers to easily share, knowledge, resources and sources between themselves for the betterment of education as a whole. Through this, especially at a global level, knowledge can be more easily shared between educators which in turn can lead to advancements in the field as methods that work for teaching can quickly disseminate across the globe.
Open education in theory also provides a safeguard against monopolies or corporate interests pervading classroom environments. Without the pressure to pay for monetized resources, teachers can more easily teach exactly what is required/wanted, without the worry of how much the resources to do so would cost.
Image taken from: https://opentextbc.ca/teachinginadigitalage/chapter/oer/, Gulia Forsyth, 2012