Is there any reason behind this? Please post answers with references.
The reason why the Friday prayer has 2 rakaats is because the two missed rakaats are replaced by two Khutbahs (sermons) which should be about current political issues of Muslims.
This is the religion of God and God has decided that we worship him in this form. The same God that has ordered to perform 4 rakaats for the noon prayer Himself has ordered us to perform 2 rakaats plus two sermons for the Jumu'ah prayer.
Well first of all in all our prayers we should do as our Messenger (peace be upon him) did:
Abu Sulayman Malik ibn al-Huwayrith said, "We came to the Prophet, may Allah bless him and grant him peace, being young men of a similar age. We spent twenty nights with him. He thought that we desired our own people and he asked us about those of our family we had left behind, and we told him. He was merciful and kind, and said, 'Go back to your family. Instruct and command them. Pray as you have seen me praying. When it is time for the prayer, then let one of you give the adhan and let the oldest of you lead the payer.
[al-Adab al-Mufrad Imam al-Bukhari]
As our Messenger (peace be upon him) used to pray jumu'a two raka'a we are asked to do so!
Now if you want to know why it is shortened looking for a secrete behind this here are some possible secrets:
- to ease for the people, as we have also two khutbas (speaches) which may take time therefore 4 raka'at would take a long time for the people!
- to make a clear difference between the Friday prayer and the dhuhr!
- as the Friday is considred as a special day (عيد الأسبوع) or the feast of each week it's more likely that the special prayer of this day should be more likely like a feast prayer (salat-u al-'id).
- And as mentioned the two khutbas take the place of the two raka'a missed from the dhuhr prayer!
By the way before the migration to Medina the prayers were only of two raka'a (in some narrations quoted by Imam Ahmad except the maghrib) and this amount was kept for the traveller but extended for the resident.
It was narrated that 'Aishah said: "The Salah was enjoined two Rak'ahs at a time, then the Salah when traveling remained like that, but the Salah while resident was increased."
[Sunan an-Nasa'i, Sahih al-Bukhari & Muslim ...]
see also this Fatwa.
And Allah knows best!