Because of the saying of Allah, the Mighty and Majestic: "Did We not give you a lifespan long enough for whoever would take heed to take heed in it? And the warner had come to you." [Surah Fatir: 37]
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Allah Almighty leaves no excuse for the person whose death He delayed until he reached sixty or seventy years of age."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6517