From that time, the Prophet (salAllahu alayhi wasalam) never went through a day without praying. Just before his migration to Madinah, he was taken on a night journey to Jerusalem and then to the heavens (Mi'raj). During this journey, Allah, Almighty, ordered him to pray five times a day. This prayer was a gift given to every Believer to enable him to experience a spiritual ascension five times a day. The Prophet (salAllahu alayhi wasalam) said: "The prayer is the Mi'raj of the Believer." It gives every Muslim the chance to communicate with his Lord."
During each prayer, the Muslim recites Surah Al-Fatihah: This recitation is not a dull monologue by the Believer, but Allah promises that it is a conversation between Him and the worshipper. The Messenger of Allah reported that Allah, the Almighty says: ‘When my slave says in his prayer: "All praise is for Allah, the Lord of the worlds," I say: "My slave has praised Me" When he says: "The Merciful, the Compassionate, Master of the Day of Judgement," I say: "My slave has glorified Me." When he says: "You Alone we worship and your Aid we seek," I say: "This is between Me and My slave." When he says: "Show us the Straight Path," I say: "This is for My slave, and I give My slave what he wants." [Hadith Qudsi]
The number of prayers in a day have been set at five by Allah almighty. The believer has no choice in the matter but to obey. To reduce the number of prayers would not only be disobedience, it would also lose the benefits of prayer.
For example, a room is only good fro residence if it has four walls and a roof. If only one wall or the roof were to be removed, what use could it be? Similarly, the prayer will only achieve its purpose and be of use on the Day when nothing except one's deeds will be of use, if it is observed in the prescribed manner.