Because of this saying of Allah Almighty: "So let them not approach al-Masjid al-Haram after this year of theirs." [Surah al-Tawbah: 28]
And this is also the view of Sa'id bin al-Musayyib (may Allah have mercy on him).
Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) sent a cavalry detachment towards Najd, and they brought back a man from Banu Hanifah called Thumamah bin Uthal. They tied him to one of the pillars of the mosque.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4330