It’s not about being lazy. Using the placeholder for the number is very important. As I explained above, there are languages where you also say “21 post”, just like you say “1 post”. If the English text used “one” instead of %{count}, it’s very easy for a translator to translate that, and then the number won’t be replaced by the actual count, which results in “one post” when the count is actually 21.
So, there is a reason why the numbers are used. See also: Always use %{count} variable when translating pluralized strings
By the way, it’s also very helpful in German because it avoids problems like this.