“Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven.” (Matthew 5:19, ESV)
Theology is the science of God, including his character, his nature, his attributes, and his law.
Every time we think or speak of God in any of these capacities, we are doing theology.
This means we are all theologians–every last one of us.
There is at least one good reason for doing good theology: to speak accurately of God.
Another one is that he is paying attention to how well we are speaking accurately of Him–in both word and deed.