visa rules (Jakarta)

I had encountered very strange situation while traveling to Jakarta from Mumbai. Even though I had my mom, wife and son's visa (all were having visa Protected content 312 for 1 year) the airline ticketing counter lady asked me to buy return ticket and didnt issue me boarding pass till I gave her the ticket number.

Can anybody let me know if do I need to have return ticket in such situation? I am very upset as I have to cancel the ticket and it involves cancellation charges.

Thnx