Fun. I have one that says smile:

No room in the back

I have never seen a thong with writing on the front what did it say?

Some need directions getting the plane into the gate.

They’re instructions

So you dont put them on backwards.

Might be the playful or vanity styles.

Because the wearer put them on back to front 🙂

Because there's not enough room on the back?

Probably because writing it on the back would be drowning in crack.