I agree whole-heartedly: the Bible is simple enough for anyone to pick up and find out exactly what he needs to do to have his sins forgiven and enjoy a relationship with Christ. But that is not all you can find in the Bible. Remember what Peter said?
And regard the patience of our Lord as salvation, just as also our dear brother Paul wrote to you, according to the wisdom given to him, speaking of these things in all his letters. Some things in these letters are hard to understand, things the ignorant and unstable twist to their own destruction, as they also do to the rest of the scriptures. (2Pet 3:15-16)
And then we have this: On this topic we have much to say and it is difficult to explain, since you have become sluggish in hearing. For though you should in fact be teachers by this time, you need someone to teach you the beginning elements of God’s utterances. You have gone back to needing milk, not solid food, for everyone who lives on milk is inexperienced in the message of righteousness, because he is an infant. But solid food is for the mature, whose perceptions are trained by practice to discern both good and evil. (Heb 5:11-14)
There are parts of God's message which are deeper, more intricate, and not quite so simple to figure out. There are places we can dig and dig and dig and still not fully comprehend them, not until we have been at it for years and suddenly a light bulb goes off. I believe God meant that to happen in order to keep us coming back for more. And continuing to study and meditate, compare scriptures and analyze them, plumb the depths of a given passage until it has nothing left to give also does this: it demonstrates to our Father exactly how much we care about Him and His Word. When was the last time you spent some time doing research on anything? What was it? A disease? A medication? A politician? A restaurant? And why? Because you really felt a need to know more for one reason or another. Shouldn't we feel that way about God too?
Your faith should not be a Sunday morning ritual, and that is all it is if you fail to open your Bible throughout the week. Under the Old Law, priests offered daily sacrifices, Ex 29:38-42; Lev 6:20. Peter says that under the New Law, we are the priests, 1 Pet 2:9. Our whole lives are the sacrifice, Rom 12:1, not just our Sunday mornings.
And one final reason to study—you have been taught a lot of incorrect things in your life. Yes, even if you "grew up in the church." I have heard more faulty arguments, more incorrect statements, and more unscriptural beliefs proclaimed in Sunday morning adult Bible classes than I have from my pagan friends. And we don't even know they are wrong!
Understand this: God will not let you into Heaven because someone else taught you wrong. …If someone who is blind leads another who is blind, both will fall into a pit. Matt15:14.
If you teach someone else something wrong, his blood will be on your head. Not many of you should become teachers, my brothers and sisters, because you know that we will be judged more strictly. Jas3:1. That doesn't mean just teachers who stand up in front of a class; it counts for anyone you talk to, even one-to-one.
Do you get it now? Bible study is important. It isn't optional. No, you may not have the capacity to be a real Biblical scholar, but isn't it odd that the one place we don't mind being told, in fact, we proclaim ourselves, the one place that we are too dumb to learn is the Bible, because we think that lets us off the hook? If that is our problem, let's work on our hearts first, then maybe the study problem will take care of itself.
He replied, “You have been given the opportunity to know the secrets of the kingdom of heaven, but they have not. For whoever has will be given more, and will have an abundance. But whoever does not have, even what he has will be taken from him. Matt 13:11-12
Give instruction to a wise person, and he will become wiser still; teach a righteous person and he will add to his learning. Prov 9:9