Disclaimer, I’ve only even seen hot dog octopuses in Anime and Manga.
Usually it’s just to be cute. In fact sometimes characters comment on how it’s childish.
I did try making them for my son once because they’re pretty adorable and he likes both hot dogs and sea creatures, and he thought it was lame at 5. At 7 he thought they were awesome.
Thankfully! My son has a dairy allergy but loves vegan cheese.