cause people have been exposed to spanish, portuguese, french and italian all their life and noticed the similarity, while few heard spoken romansh, romanian or ladino. Romania (and moldavia) were behind the iron courtain until yesterday.
Also, as an italian, while i find it possible to understand written romanian, it's much harder to understand it spoken, as the slavic pronounciation is very different.
On the other hand, Romanians often find it very easy to understand Italian, more so than most other latin languages. I know I do, I can watch Roberto Benigni films and mostly understand everything, without ever specifically learning italian (but Italian/English subtitles do help).
Also, as an italian, while i find it possible to understand written romanian, it's much harder to understand it spoken, as the slavic pronounciation is very different.