Why is that?
...I am female!

You can have a ton of fun in Singapore. It just depends on what you are after.
I know quite a few single female (European looking) women that have a great time in Singapore. Most will end up making friends with friendly locals... and many make friends easily in what expat community there is.
If you are wanting lots of dates and male attention though it may not be what you expect.
In Singapore guys (only requirement most of the time is to have a wallet with some cash in it) can get laid A LOT. Anytime of day or night just walk down the street and you can and will get propositioned.
Believe me, it happens A LOT. There are so many 'working girls' its rediculous and many are absolutely beautiful. Its just there. Its the nature of the place.
If one is not into the whole multitudes of working women who are quite aggressive, even the local non working girls generally have small little hot bodies and are pretty likely to put out if one has any game whatsoever.
Put yourself in the position of a guy... you come from overseas... where (in my opinion) many females are quite feminist and are normally rude and quite demanding in one way or another.
You show up in Singapore, walk down X street and get hit up to get laid 3 times on one walk. I personally have been hit up for it on the bus, on the MRT, while walking down the road, in malls, and even while eating dinner once. And these girls were NOT ugly. In fact quite the opposite.
If you are in the guy's shoes what would you do?