Here's why:
* No census: J.K. Rowling never provided a concrete number.
* Widely spread: House-elves are found serving in a wide range of households, from wealthy pure-blood families to humble Muggle families.
* Unknown population: We only see a small sample of house-elves throughout the books, mostly those connected to Harry Potter.
Some estimates:
* Hundreds, possibly thousands: Given the vast wizarding world and the prevalence of house-elf servitude, it's likely there are hundreds, if not thousands, of house-elves.
* Many are undocumented: Some house-elves may even be unregistered, especially those serving Muggles or in isolated areas.
Key takeaways:
* The exact number of house-elves is unknown.
* It's reasonable to assume a large population based on their widespread use.
* The books focus on a small sample, not representative of the entire house-elf community.