Parents Visitor visa application denied twice at Mumbai consulate

[acer]

Hello,

Last Month, my mom and dad attended visa interview for second time and got denied. I am currently in USA from last 7 yrs after completing my M.S. Not sure what reason is ?
Last month i was in India, so i was help my mom and dad to travel to Mumbai for interview.

Below questions were asked
1) Where is your son? My mom answered :- He is in USA but currently he is here for visit
2) Why you are going to USA ? My mom and dad answered : For Visiting different places like SFO, Vegas, NY etc
3) Who is here at home in india ? My mom and dad answered : My younger son

and denied Visa again without any further questions or without asking for any documentation. During their first Interview also no documentation were asked.

Not sure, what is reason. Is it because i was in India ?

Question:
Should i ask them to go for interview after 6 months ?
Is it worth giving try again ? Because visa is denied twice
I am not married yet but should i wait for my wife to come here?

Please help.