Theistic evolution simply states that the science of evolution is true and affirms that, like all other areas of nature, God is the One behind those natural processes and mechanisms.
The reason why a term is required ("Theistic Evolution" or "Evolutionary Creationism") is because of how often many Young Earth Creationists misunderstand Christians who are fully accepting of the science of evolution--some accuse us of rejecting the fact that God is the Creator, or accuse us of removing God from the picture which simply isn't true.
If the same were true with things such as gravity then "theistic gravitation" would likely be required to assert that gravitation is a natural force in the universe and the science behind it is sound and that we, in faith, believe God is the One who established the natural mechanisms and processes behind it.
The key difference is that there isn't a sizeable misinformed movement claiming gravity to be evil, accusing "gravitationists" of having an agenda to remove God from the picture and the like.
-CryptoLutheran