Shoe covers at temples are not souvenirs.

No, you do not get to keep them.

In most temples, mosques, or other sacred sites where you remove your shoes, the plastic shoe covers or loaner slippers are strictly temporary. You hand them back when you exit, or you toss them in a bin. They are meant for hygiene and respect, not as freebies.

If you are visiting a place that sells souvenir sandals (like traditional geta in Japan or woven palm sandals in Southeast Asia), those are a different thing entirely — you buy them in a gift shop. The ones handed to you at the entrance are disposable or reusable for the site only.

Treat them like a library book, not a gift.