This is because the sound "w" is typically created by a single "w".
However, there are some exceptions, such as:
* "Awww": This is an interjection expressing affection, sympathy, or surprise.
* "Whew": This is an interjection expressing relief or exhaustion.
* "Wow": This is an interjection expressing amazement or admiration.
These are often considered to be "informal" or "colloquial" spellings, though.
Let me know if you'd like to explore any other letter combinations!