We South Asians are programmed to believe we are incompetent to take responsible decisions. You get to see this kind of parental conditioning in all areas of life - what we wear, believe in, graduate in, etc. We might be 27 but we still are kids for our parents, who think they know better than us (and so do we) as they equate age with maturity. Parents also feed us with an unhealthy dose of responsibility, respect and gratitude (and guilt) that they use to manipulate and suffocate our wishes. Any act of independence is construed as defiance, disrespect and ingratitude to their years of love and sacrifice and is followed by rivers of sorrow. 'Children' eventually give in.
Moreover, we don't want to take responsibility for our actions. Those who want to marry for love, don't because if something goes wrong, they would be blamed and have no one for support (as their parents would have ostracized them). If marriage's arranged by parents and things turn sour, parents are to be blamed. Some put the blame on parents either way.
Most women are financially dependent, unqualified, uneducated and at greater risk if they choose to go against parental arrangements.They are perceived as objects to be passed on from one man (father) to another (husband) with no right to decide for themselves. Most men stay in the same house as their parents and fear having to let go of stability and property. There's a group of parents that tries and controls every aspect of their adult child's life as they depend on them for monetary support (particularly in a man's case). Not only do they control the son but also the daughter-in-law. An independent daughter-in-law threatens to snatch away their support system. Some women are told only about evils ('use' you, trafficking,etc.) of interacting with men.
In a collectivist society, stigma is a major influence. What would the society think about their family if a person elopes or marries into a lower caste? Public shaming! Dating doesn't guarantee a ring and can lead to a bigger stigma - pre-marital sex. It is assumed that two people in a romantic relationship are sexually active (or would become) and parents, especially with daughters, think this renders their child 'unmarriageable'. It is also assumed that people fall in love with each other after marriage so dating is pointless. Besides, we are trained not to think. Education doesn't really matter here because it's largely rote learning. 'This has been happening so it must be the right thing. Our culture is the purest and the best. We shouldn't let degenerate values seep in'. Honour killing is another major issue, particularly in underdeveloped/undeveloped areas.
Media plays a role in reinforcing such value systems. Most daily soaps portray women as lacking career-orientation, fulfilling only domestic tasks, married to near perfect spouses (chosen or approved by parents) or even if the spouse is evil, they change him into a better person. Villainous 'cheap' women keep villainous boyfriends who end up with a ghareloo 'sanskari' wife - who they begin to truly love .
It's important to remember that the Indian society largely doesn't accept cross-sex friendship, leave alone dating. Even in schools, if a guy and a girl want to sit next to each other, teachers have a problem. Most adult women and men have little to no experience when it comes to dealing with members of the opposite sex (other than relatives) and feel awkward in situations that bring them face to face with each other. They are taught to accept whatever parents decide for them and see no need for change. Divorce rates from countries where people marry for love are quoted as proof that 'arranged marriage' is better than 'love marriage'. No one is told why arranged marriages don't fail that often.
Apart from that, for a person (who is okay with ''love marriage') to marry their lover, the lover too should be willing not to let parents dictate. There's a dearth of such people so the former person goes for an 'arranged marriage'. Homosexual men and women have no choice but to marry for convenience.
Obviously, in some families, 'love marriage' is the norm. In some, children go against traditions and marry. In some parts of India, 'arranged marriage' system isn't that prevailent. However, these still comprise a minority.
In my opinion, love doesn't mean a marriage will work out nor does convenience mean it won't. People marry for different reasons - money, fear of loneliness, sex, legitimate children/own blood, parental satisfaction, etc. Not everyone marries for love. Marriage requires a whole lot of qualities to sustain. People,outside South Asia, do select partners based on race, income, religion, job profile, nationality or beauty. Why pretend only South Asians are superficial?