Why some shows missing the fanart background ?

Does anyone know why some anime have large fanart backgrounds (like banners or cover art) while others don't?

For example, why does Sousou no Frieren have a large background for Season 1 but not for Season 2, whereas Jigokuraku (Hell's Paradise) has them for all its seasons?

Is this an issue with Otaku, fanart availability, or the skin itself, or something else entirely?

Thanks in advance!