Please read this post from ms514 ji in 2011
VAHEGURU JI KA KHALSA, VAHEGURU JI KI FATEH
There is a lot of power in symbolism beyond mere practicality. Where Guru Sahib is Parkash, there is a canopy. The canopy's original intent was to protect whatever/whomever was underneath from the elements and was a status symbol of someone important/royalty. The chaur was originally a fan/fly whisk, used to fan and keep the flies away - one who had an attendant doing this was obviously someone with great power. The throne elevates whoever/whatever is on it from everyone else, granting it status above that which is common. Such symbolism was present for royalty or persons of great importance prior to Guru Sahib being sent to this world. So the Chaur Sahib, The Chandoa Sahib and the Takht Sahib have become the triumvirate insignia of royalty present in the Gurudwara. In fact, the court of the King of Kings is even referred to Darbar Sahib, or the King's (of Kings) Court. Though the practical, utalitarian functions of the three symbols of royalty present wherever Guru Sahib is may not be necassary anymore (enclosed buildings with climate control, pest control, electric fans), their symbolism and the status that they imply are of prime importance. Such symbolism is not lost even on politicians in the present day - when presidents and prime ministers speak from an elevated platform and have a podium with their official seal, the inherent symbolism grants them a status above and beyond the common man/woman.
Similarly, sprinkling of water, playing of bells/horns and other rites when transporting Guru Sahib are the means of broadcasting that royalty is proceeding down a path. Consider that the road around Buskingham Palace is red, denoting that the road used by the worldly royals is to be given a unique status from other roads. Sprinkling of water/washing the path/sweeping the path designates that that which is to traverse the said path is of great importance, even if the utalitarian action of washing/sweeping itself may not be as vital as it was in the past. The symbolism implies the royal status and what is more royal than Guru Sahib? The use of milk and water was (and is) that they possess the power to purify and wash the area on which they are used. They purify the way for whatever/whoever is to proceed over it, as their very feet deserve the utmost in purity and cleanliness. So water is used (and is can be used to wash the path, but has commonly been relegated to the symbolic use that the way is being made pure as that which is to follow in the path of the water is also pure and of high status) in its symbolic capacity (though again, it can and is used for its utilitarian purpose as well. I witnessed a Nagar Keertan in which the Sangatan had obtained a water truck, watered the road and had Sangatan sweep the entire route of the Nagar Keertan after the water truck passed - 6 miles - for Guru Sahib and the Sadh Sangat. Vah! Dhan Tere GurSikh!).
So symbolism is very vital in establishing and making it apparent that Guru Sahib is of the highest royalty. They are the visual indicators of royalty to the rest of the world and the means by which all can provide the minimal respect that is accorded to Guru Sahib (the supreme respect being to ensure the symbolism exists and is provided for to the best means possible, but to also read, understand and follow what Gurbani says - that is the highest form of respect. Otherwise, we are like the children who put expensive blankets on our elders, but never talk to them or follow their advice).
Bhul Chuk Maaf.
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥
