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).
Another Romance language I found out about that exists unexpectedly in Eastern Europe is Aromanian. http://en.wikipedia.org/wiki/Aromanian_language Most other Romance languages are regional languages in a Major romance language dominated area (such as Occitan/French, Catalan/Spanish). This one, on the other hand, is a romance language surrounded by Slavic and Greek languages.
Relevant linguistic map: https://en.wikipedia.org/wiki/File:Romance_20c_en.png