From MDN:

> Note: While <input> elements of type button are still perfectly valid HTML, the newer <button> element is now the favored way to create buttons. Given that a <button>'s label text is inserted between the opening and closing tags, you can include HTML in the label, even images.

It's a thing from the times when <button> did not exist. Other use cases were for supporting IE. Today just use button.

I would literally never use <input type="submit|button"> for anything when the <button> element is an option, personally.