What is the necessity of worshiping idols in temples?A.
Idols or images of God are inert objects. A form carved in a stone or painted on paper is an imaginary form and is not even a direct photograph. Idols and images are only models representing certain concepts. They facilitate knowledge.
The form of idols and photos is mainly human. This represents the concept that the Lord always comes to this world in human form as is said in the Bhagavad Gita (Manusheem Tanu Mashritam...). Please remember that the Gita did not say that the Lord would come in any other form. The forms of fish, tortoise etc., which the Lord took, as mentioned by the Puranas were only temporary. They were meant only to kill some demons and nobody worshipped such forms even during their time. Rama, Krishna, etc were the human forms of the Lord. They were worshipped by several devotees like Hanuman and Gopikas in their time and are being worshipped even today.
The Lord will come in every human generation; otherwise, He would be accused of being partial to a particular generation or age. The Lord comes whenever there is a necessity as said in the Gita (Yada yadahi). Once this concept is realized, there is no need of going to the temple and worshipping idols One should go from school to college and then to university. This does not mean that when one leaves the school, the school should be destroyed. The school must exist for others who need it.
Similarly, if for one person the idols and the images of God are not necessary anymore, it does not mean that the idols, photos and temples should be destroyed. They should be protected and must be respected as the models of divine knowledge for the ignorant devotees who need them. Some devotees cannot accept the human form, which is before their eyes as said in the Veda (Pratyaksha dvishah). For such devotees, idols and photos are necessary for meditation since they are still at the high school level in spirituality. Idols and pictures are useful for meditation for such limited minds as said in the Sastras (Pratima svalpa buddhinam).
The Veda says that the Lord does not exist in inert objects (Natasya pratima, Nedamtat), but It says that inert objects can stand as models representing the Lord (Adityam brahmeti). Therefore seeing and meditating upon idols and photos are acceptable in the case of ignorant devotees. However, a lot of other rituals like offering food, burning camphor, fume sticks, oil lamps and breaking coconuts and offering flowers are not mentioned in the Vedas and are unnecessary. These unnecessary rituals should be avoided especially since many of them cause pollution and harm humanity. Offering food should be done to the human form of the Lord only, where it is befitting and not to the inert idols. Ijya or yajna is cooking and offering of the food to God. The Gita says that such ijya should not be done to inert objects.
In the name of idols, some people are actually stealing food and money. Everyone knows that idols and photos do not take the offering whether it be food or money offered as gurudakshina. It is people in and around the temple who take the offerings. Most of these people are either use the money for their selfish ends or waste it due to their ignorance. Whatever gurudakshina is received from the devotees should be given to the priest and not the managing committee of the temple. The business of the merchants selling materials for worship within temples should be stopped, because such materials are not even heard of in the Veda. Of course, the priest should be a Sadguru and preach the divine knowledge to the devotees and the devotees should give gurudakshina to such a Sadguru alone. Thus, the temple should become a center of learning selfless devotion and divine knowledge and the priest must do only jnana yajna (propogation of knowledge) in the temple and not the dravya yajna (burning food and other materials in the traditional fire ritual).
It is said in the Gita (sreyan dravyamayat). The Gita condemns ijya of inert objects because such ijya is only a business and is a fraud. Devotees who perform such ijya will be born as inert objects (bhutejya yanti). Such devotees come to the temple in order to cleanse themselves of their sins. The sins have been actually perfromed by them. The come to the temple and perform some fire rituals, burn some food and other materials, give a donation to the priest and assume that their sins have been cleansed. They now expect to receive some 'good results' since they have done those traditional rituals. Good results are given as the fruit of good actions. Burning food and materials in fire cannot classify as good actions deserving good results. Therefore this business, which involves the removal of the bitter fruits of sins actually performed and getting of sweet fruits of good deeds which have not been performed at all, is a big fraud.
All this is false. The theory of karma says that one has to suffer for all his bad deeds and can never get the result of any good deed without actually performing it. (Avashyam anubhoktavyam...kalpakoti shatairapi). The real spiritual path should be preached in the temple which is niskama karma yoga i.e., sacrifice of work and sacrifice of the fruit thereof (money) to the Lord without aspiring anything in return. Remember, that only the ijya (burning of food and materials in the ritual fire) is condemned and not the temples or idols, which are the models of the divine knowledge.
Source - http://www.universal-spirituality.org/rituals.html