Great question!

"I am not saying that Catholicism is false, but why would a Christian not obey the ideals of Sola Scriptura? The Bible is the only reliable word of God."

Because Sola Scriptura is:

1) Illogical
2) Unhistorical
3) UnBiblical

It's illogical because it is circular reasoning, and thus a fallacious epistemology. You cannot take a book as authoritative without circular assumptions regarding the nature of that book. Moreover, when you take a book like the Bible as "sole authority," what you're really doing is saying that YOU are the sole authority, because the reading of a book like the Bible involves interpretation. When an individual claims Sola Scriptura is their rule of faith, that means their personal interpretation of Scripture is their rule of faith. Hardly logical.

It's unhistorical because no one prior to Martin Luther considered the Scriptures to be the sole word of God. Christians for 1500 years understood that there was Scripture, and it was valuable and important, but there was also Tradition, of equal importance and value because it is the mate of Scripture, it's Christ's teachings passed down orally. Without both, there's no way to check an interpretation for errors. Likewise, it's unhistorical because it neglects the entire period wherein Christianity existed WITHOUT the Bible as we know it. Christians had Scriptures, but they weren't a set canon, and they differed by region. And particularly early on, there wasn't anything written in the New Testament. Even the earliest estimates would have it seem that for a decade after Christ's death, nothing was written of the Gospel. And that's the early estimates, not the late ones. How is it the historical practice of Christianity that only Scripture can be relied upon?

And finally, Sola Scriptura is unbiblical. NOWHERE in Scripture is there any indication that Scripture is the sole authoritative source for Christian doctrine. Nowhere. It's absolutely and completely impossible to demonstrate Biblically, making Sola Scriptura a contradiction in terms. If all Christian doctrines must come from the Bible, that's a Christian doctrine in and of itself. Yet it is not Biblical. Sola Scriptura fails according to its own test.

Now, I'm certain you're going to give me the verse from 1 Timothy about Scripture being inspired, profitable for teaching, correcting, debating, etc.

But this verse says nothing about Scripture being 1) sole or 2) authoritative. It says that Scripture is a useful resource that's inspired by God. I agree completely. But that doesn't make it the sole authority for Christianity. And it technically leaves us with the problem that the verse itself, written as it was before most of the New Testament, refers to the Scriptures of Timothy's youth. The Old Testament. It leaves us with absolutely no way to know WHICH books are to be part of Scripture, either Old or New since, again, neither had a definitive canon at that point in history.

Lastly, the Bible DOES have certain things to relate concerning what is to be our authority after Christ ascended into Heaven. The Bible never mentions itself, but it does mention the Church. Christ never mentions leaving a Bible. Christ does talk about leaving a Church. Thus Sola Scriptura fails its own test again.