Obter toda a data do mês junto com os dados da tabela

A propósito, você não precisa do join em user_profile.

Se você tiver dates tabela com as datas relevantes, isso é muito fácil:

SELECT dates.day AS `Date`, COUNT(DISTINCT ts.user_id) AS user_count
FROM dates
LEFT OUTER JOIN tracked_search AS ts
    ON ts.created = dates.day
GROUP BY dates.day;

Como você provavelmente não tem um dates tabela e pode não querer criar e manter uma, você pode usar uma das soluções para gerar a lista de datas em tempo real. por exemplo. Obter uma lista de datas entre duas datas ou Como obter uma lista de datas entre duas datas na consulta mysql select

SELECT dates.day AS `Date`, COUNT(DISTINCT ts.user_id) AS user_count
FROM (
    SELECT ADDDATE('1970-01-01', t4.i * 10000 + t3.i * 1000 + t2.i * 100 + t1.i * 10 + t0.i) AS day
    FROM (SELECT 0 AS i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS t0,
         (SELECT 0 AS i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS t1,
         (SELECT 0 AS i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS t2,
         (SELECT 0 AS i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS t3,
         (SELECT 0 AS i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) AS t4
) AS dates
LEFT OUTER JOIN tracked_search AS ts
    ON ts.created = dates.day
WHERE dates.day >= '2017-10-01'
AND dates.day < '2017-11-01'
GROUP BY dates.day;