if I start with 0.01 BTC I would aim at a relatively high amount of 0.1 BTC and then withdraw, the issue is not withdrawing but not re-depositing the amount later and playing it again until losing that money, which is very difficult to avoid when you have the urge to gamble in addition to bitcoin in your wallet...

Of course not!, specially if your profit is something significant and a multiple time your deposit, it's always good to know when to leave gambling when you are ahead and gambling your profit aiming for more has cost most gamblers big money losses, it's better to quit gambling when you are ahead.

I do sport betting regularly when I've funds, but I did try trading between BTC and USD, The major exchange I was using for that a year or so ago was bitstamp which later put restrictions on my country, don't like the interface of BTC-E nor it's reputation so stopped trading.

These are not the only field BTC is used in, as BTC is now widely used in almost any market (from gold bullions to buying refreshments in local stores), BTC is good for porn, gambling for it's private nature, since people find these embarrassing most of the time. Drugs are because of anonymous nature, since these are illegal.