NB: one can be well-versed and familiar with theology and be a good student of it, be talented or excel at it in seminary, and still hardly know the Lord, because one doesn't apply what one learns. We are all theologians, it just is a matter of what kind of one we are.
Theology is often called the queen of sciences because it is a search for truth that predates the scientific method (or scientific empiricism) laid down by Sir Francis Bacon. In short, you must be willing to go where the truth leads you and keep an open mind ("If any man wills to do His will, he shall know of the doctrine..."), and be as unbiased as possible (total objectivity is impossible to achieve). Theology has been called "God-talk" because it is literally the study or "ology" (Greek) of God or "theos" (Greek). Spurgeon says that the proper study of the Christian is the Godhead. He adds that nothing will so expand the intellect or humble the mind that the study of the Deity.
An ancient Greek philosopher was asked to describe God: He couldn't come up with one, needless to say. In the Bible we get no adequate description of God, they help us know Him--other so-called holy scriptures do not do the job. It is really an exercise in futility to make speculations about God--we must rely on special revelation as the Bible claims it has. What is God like becomes the million-dollar question? We engage in mental gymnastics to ponder the depths of God: There is no higher science, loftier speculation, or mightier philosophy. J. I. Packer adds that in the 17th-century theology was the hot topic and every gentleman had this as a hobby. People used to be well informed of what the Bible taught.
Is theology just theoretical? No, it has practical applications too. We study the holiness of God to see how to be holy and what God expects: to always do the right thing (Mother Teresa of Calcutta says that "holiness consists in doing the will of God with a smile." We must study God to learn to be godly and knowing God keeps us in touch with reality (we often need a reality check). "What you think about God is the most important thing about you," according to A.W. Tozer. The most important thing about us is our character and I believe the most important aspect of that is our integrity--God isn't necessarily trying to change our personality, but our character. God's character or the sum total of His attributes shows us how to have godly character. We are to imitate God and emulate Jesus: "What would Jesus do?"(WWJD?)
So who needs theology? It is paramount to our getting to know God. However, knowledge about God is no substitute for knowledge of God and it can remain purely theoretical if we don't apply what we know. We must learn to contemplate the Deity and meditate on His attributes as we interact personally with Him to get to know our personal God. Soli Deo Gloria!