Simple: biological risk management
We pretend we are highly sophisticated as a species but we are still biological beings a few steps removed from monkeys.

We are certainly capable of rational thinking, but that takes effort and most of the time we actually DON'T think rational.
Most of the time we are on a biological auto pilot which goes like this:

What you know probably won't kill you, if it did not harm you yet. Keep doing it.
What you don't know might kill you. So stay away.

That's how our brain works, but it is very bad at statistics.
It is what causes health crises, financial debt, staying in dead end jobs.

Read Daniel Kahneman's Thinking, fast and slow. It is not easy reading but it is a pretty practical operating manual for your mind.

Discovering new things can indeed be beneficial but keep in mind that your "mind" has to actively work at rational thinking processes. It takes concious effort until the "new" becomes "familiar" and then you probably established a new habit.