White sage is typically used since that is the species used by the Native Americans the smudging ceremony was adopted from. Other plants are used for the same or similar purposes elsewhere. For example, in the south-east US, rabbit tobacco is used for similar reasons.
But there are also things missed from the Native American tradition -- and yes, this falls completely under belief -- such as their teaching that sage smudging only removes energy. The space must also be made ready for and then made to invite the good energies/spirits/etc. There are Native groups who believe that just smudging with sage will leave a place vulnerable for any entity which wants to occupy the space. It is why ceder (typically American red cedar; sometimes some species of juniper are used) and sweet grass are also used in their ceremonies: They purify the empty space, and invite the good spirits to come in.
It's also why the Native American practice of smudging is also fund listed with rituals of "bringing light" into every corner of a dwelling: The light is symbolic, and is used to clear the space of all negative energies, that is leaving nothing undiscovered. Many of these which I have read include subsequent practices of ritual or prayer to invite what is wanted into the dwelling.
The same practice is mirrored in some Christian traditions, with blessing a house, casting out whatever negative things may be there, but followed with an invitation to God, angels, etc.