Why are mermaid 2's and 3's popular all of a sudden?

[Tohrukun]

i've seen a few threads in the past week of people looking for them

guys i just wanna collect mermaids in peace lol

 

[Champ]

Lol I gave mine away for free

 

[JAYY]

I'll give you 1x mermaid2 and 5x mermaid3 in exchange for your mermaid secret heh

 

[Goddess]

I don't know but I've loved Mermaid 1 and 3 since I saw them. I have 2 mermaid 3's now that I pulled from the SitS.