It's probably due to picking up these phrases from American TV or films, or switching language to add emphasis or nuance to a phrase, and it's not surprising because of Swedes' high level of English: switching between languages, also called code-switching, is common among bilinguals across the world. Prepositions are the little words like 'on', 'in', and 'from' or 'på', 'i', and 'från' in Swedish, and while they're usually small words, they can cause big problems since their usage varies from language to language.