Partly, upbringing. One learns whatever degree of trust in the scientific community from family, teachers and other connections, before they learn to judge the scientific community's claims.
Whatever you do, do it in faith. I am a TE. But the first 20 or so years of my walk I was a YE. I just find the TE more realistic and in tune with the nature of God and creation as we see it.
Personal bias, upbringing/culture, and peer pressure. Genetics may play a certain part in the way people think as well.
Question one and two cannot really be answered truthfully because there are reasons based on many factors. Culture can play a part, People’s belief in God or whether they are an atheist. Some rely only on scientific explanation, and there are some religious groups that teach evolution. So these groups need to be studied for the many reasons for either.
I was on both sides of the argument in my life. The YE proceeded from a lack of knowledge of both what TE teaches and what the Bible teaches. From where I am now, I see very little in TE that can successfully countered. But I am always looking for good information. I have learned that problems just provide us opportunities to get better and more knowledge.
