A while ago – long before they filmed the Last Jedi – a friend of mine visited the island Skellig Michael, which is the Irish island that was the setting for Luke Skywalker’s hideout in the Last Jedi. One thing that immediately impressed them was the the island was literally covered with Puffins. They were everywhere. You couldn’t avoid them. That’s why there are Porgs: it was cheaper to digitally create the Porgs to cover the Puffins than digitally remove the omnipresent birds. You couldn’t physically remove them because, you know, pesky laws.
For the record: Hieronymus Flibble absolutely HATES Puffins. He considers them his arch-enemy. As a result, he also hates Porgs.. Despises them. Refuses to watch the Last Jedi as a result (and I’m not allowed to even have the DVD of the movie at the house).