None offer a developed Christology or Trinitarian theology.
None explain their views on the relationship between God's sovereignty and human free will.
None explain their view regarding gender roles, or the lack thereof, in their church or in society.
None state what they believe about any major social issues, such as abortion (or the death penalty, or euthanasia, or war, etc), let alone why they believe what they do or offer a consistent system with which to judge other ethical matters.
None of them even list out which books they accept as the Bible.
I could go on.
(Amazingly, many evangelicals think that this is a good thing, that they have avoided the dangers of dead theology.)
But here is my question: What do they believe on all of these issues, as well as many others? If an issue isn't mentioned in their statement of faith, is it open for disagreement? (If so, are all of the issues I listed above open for disagreement in those churches?) How does the pastor know what to preach on Sundays? Of course, they want to preach the Bible. But the teacher's job is to interpret. That's why churches have teachers in the first place. Churches could just have someone read Scripture aloud every Sunday in place of the sermon. We have teachers to give us the interpretation. Theology is complicated. It's not always immediately obvious what the Bible teaches on a given issue. Someone needs to bring it all together.
Let's say you have a question about one of the many things not covered in the church's statement of faith on their website. You go to your pastor for an answer. The pastor might have an opinion, he might not. He might be somewhat educated on the issue, he might not. There might be disagreement within the leadership of the church on the issue. It might be something that no one in the church had even talked about yet.
Let's say you get an answer. What if that particular pastor retires or leaves? The new one says he agrees with the church's written statement of faith, but he might disagree with what the previous pastor taught that isn't in the statement of faith. I guess the church teaches something different now.
Churches are placed at the whims of whoever happens to be teaching in them.
I anticipate two objections.
(1) Catholic priests don't always preach in line with what the Catholic Church officially teaches. This is true. But at least the Catholic Church has a foundation, something solid, something with which one can judge whether a priest is teaching what he is supposed to be teaching. Most evangelical churches lack this almost entirely.
In other words, they make it up.