Think about it.  If you halt trading and withdrawals, your customers really are trapped.  They'd have lawyers barking up their asses in no time.  This at least gives them the impression of some freedom.  Also, and most importantly, the exchange would bring in no money while trading is halted.

When you think about it, this is an incredibly clever move on Gox's part, at least in the short term.  You've got a bunch of frenzied traders beating the crap out of each other and Gox harvests the spilled blood.  Only Gox insiders can withdrawal to arbitrage, and I guarantee you they have.  Who the hell do you think gets to "beta test" these changes?  MK's cronies.  This is little more than a swindle, whether it was intentionally done or not.

The biggest problem cryptos face isn't technological hurdles, it is human meddling.  Technology will eventually grow to a point where it is insulated from such factors, but it will take many years of evolutionary code changes.