Why does only Misty seem to care?

About Natalie and Lottie dying. Shauna, Van and Tai seem only slightly sad about both but it doesn't seem to affect them at all, and they brush it off quickly.

Tai did not care at ALL about Lottie's death.

Misty is understandably sad about both. Why is no one else? Is it just that they drifted apart as adults?