I think because romantic relationships require more...investment, is the word. And sometimes, one person in a romantic relationship might realize they're not ready for said investment and commitment, and they just might feel rushed.
In platonic relationships, it's easier cause things are more...relaxed, I guess.
For myself at least, I’d be better off with just friendships, they’re easier. Romantic relationships are just not my cup of tea.
But, you know, I’m just speaking from personal experience.