Sometimes, loanwords sound simply cool and modern, and traditional words are too mundane or too direct. English speakers also have imported many new loanwords from foreign languages (café, siesta, kaizen, ...), but generally speaking, the influence that English has on other languages is much stronger than that in the opposite direction.
Semantically, キッチン, ベッドルーム and バスルーム are synonymous with their traditional (kanji) equivalents. However, these modern katakana versions tend to be preferred:
- when the room is western-style (洋室),
- by young speakers,
- in metropolitan areas, and
- in business scenes, especially in ads.
The more of the above conditions are met, the more the katakana versions are chosen. On the other hand, older speakers living in traditional Japanese-style houses still usually use 台所, 寝室 (or 寝間) and 風呂場 in daily conversations.
There is another Japanese-specific reason to prefer katakana over kanji for some words. See my previous answer.