Forgetting is yet another consequence of our fallen nature as a result of sin. An unfortunate but common hardware failure that can impact some more than others. But the spirit of forgetfulness is a much deeper matter because it's not something occasional; but rather, a trend. This is a pattern of neglect that is not so much in the mind as it is in the heart because it's rooted in a lack of belief; a failure of faith in who God is. I'm not talking about not believing if He exists or if He is indeed the Most High. But believing in who He is in His character; even, in His heart.
If I don't believe in who God is in His character, how can I believe in what He says? If I don't believe in what He says in His Word to Israel, how can I believe in what He says to me individually? In short, not reading ultimately comes from not believing which leads to not needing.
I'm not sure what the weather is like where you are today, but let's pretend that today it is NOT raining and not even forecasted to rain. You don't see any clouds, the sky is clear, and the sunbeams are blasting. So if I were to come your way and ask you why you don't have an umbrella, you would probably simply reply, "because I don't need one." When the Word becomes an afterthought, it's because we don't believe we need it. It's not a matter of questioning it's existence or power, any more than not having an umbrella doesn't mean I don't believe in rain, storms, or the Weather Channel. But when God becomes an afterthought, it's a sign we have gotten to a place where we don't think that we need Him.
Neither have I gone back from the commandment of His lips; I have esteemed the words of His mouth more than my necessary [food]. - Job 23:12 KJV
Thy words were found, and I did eat them; and Thy Word was unto me the joy and rejoicing of mine heart: for I am called by thy name, O LORD God of hosts. - Jeremiah 15:16 KJV
As newborn babes, desire the sincere milk of the word, that ye may grow thereby: - 1 Peter 2:2 KJV
Please don't leave this thought just focusing on how much you do or don't read the Bible. You will leave either proud of how much you do or discouraged about how much you don't. What we really need is the LORD Himself to reveal to us is how much do we see our need for Him. If you know how much you need Him, you will always take time to read Him!
God has something to say to us (more than we want to hear it)! That's why there is always a WORD!