Mass public transport run by private companies

Whenever SMRT and SBS Transit want to raise fares, reasons given are always "rising operating costs" or "have not adjusted fares for 2 years".

I wonder the rationale of allowing private companies operating the public transport here. I recalled the reason given was that private companies "are more efficient", but having monopoly over the industry, they have no motivation for efficiencies, because instead of re-looking at the efficiencies of their own operations, they usually choose the easy way out of passing the costs to passengers. Why? Because they know we can't run away from them. No matter how much they raise the fares, we still need to take the transport.

Mass public transport is a necessity for most Singaporeans, and forms a very important part of the basket of goods for commoners like us who cannot afford our own private transport. Yet we are at the mercy of these 2 sole operators who have no competition and are very much in a very cushy comfort zone. We see their profits rise year after year, with a big chunk of it attributed to the fare increases which burn a deeper and deeper hole in our own pockets with every fare increase.

They justify fare increases (and thus fat profits) so as to answer to their shareholders, but who can we justify our increased costs to?