Why do friendships turn into relationships?

What are the reasons behind this? How does it happen? Why does it happen?
I mean, I have heard about things like this in the past but I have never quite understood the logic. Lol.

When Friendship grows to level 25 by gaining experience in battle, it turns into Relationships through evolution. This usually happens directly after the battle ends and you'll receive a notification as it's about to happen. Nobody's really sure why it happens, but many pokémon professors have devoted their lives to this process.

(If you think your friendship is too valuable and you don't want to risk things changing too much with relationships, you can cancel the change by holding down the B button. Unfortunately, you'll have to do this every time Friendship levels up.)

I honestly don't know why but I wouldn't recommend it as it's difficult to remain friends after a break up especially if you still have feelings for the other person and they've moved on.

Agreed. On one hand going out with someone you start out as a friend with is great, because they probably share your friends. They get the jokes, and they generally like the same stuff. And then you break up, and it's awkward and horrible.

when friendship grows to level 25 by gaining experience in battle, it turns into relationships through evolution. This usually happens directly after the battle ends and you'll receive a notification as it's about to happen. Nobody's really sure why it happens, but many pokémon professors have devoted their lives to this process.

(if you think your friendship is too valuable and you don't want to risk things changing too much with relationships, you can cancel the change by holding down the b button. Unfortunately, you'll have to do this every time friendship levels up.)