なぜ「cin」はユーザー入力の最初の単語だけを読み取るのでしょうか?

#include <iostream>
#include <string>

using namespace std;

int main()
{
    char x;

    cout << "Would you like to write to a file?" << endl;
    cin >> x;
    if (x == 'y' || x == 'Y')
    {
        string response;
        cout << "What would you like to write." << endl;
        getline(cin, response); // Use getline instead of cin >>
        ofstream file;
        file.open("Characters.txt");
        file << strlen(response) << " Characters." << endl;
        file << endl;
        file << response;

        file.close();

        cout << "Done. \a" << endl;
    }
    else
    {
        cout << "K, Bye." << endl;
    }
}