People do not like change, but need diversification? Is that not contradictive? People generally resist change, yet they have a desire for diversification.Of course, both is possible. Just like the need of safety but the desire for new discoveries and adventures.

But what is the psychological explaination? Is there anything I misunderstood?
Balancing a combination of 'sticking with what you know' and 'exploring new things' is optimal in a lot of environments. What the optimal balance is depends on a bunch of factors like your planning horizon, the distribution of good things in the world (common/rare &amp; similar/dissimilar), and how you interact with them (reusable, like a shortcut, depleting, like a gold mine, or one-shot interaction like buying a house).

People are really surprisingly good at this! Fun search terms for google scholar might be "explore/exploit tradeoff" or "multi-arm bandit problems" [with humans]. But it's a big and complicated literature, actually I'd recommend starting with a popsci version, "Algorithms to live by" by Brian Christian and Tom Griffiths. I think you might enjoy it, it's a great book, very readable, and it goes into some detail on this question and a few of its near neighbors.