The original method serves its function correctly: it acts as cash. Nothing inherent in cash allows you to un-spend it if you didn't get what you paid for. (The legal system can force someone to give cash back, if you can track them down, but BitCoin intentionally makes that difficult or impossible depending on whether they take steps to preserve their anonymity.)

Escrow services exist in the real world, too, for much the same reason: holding party A's cash and party B's item until the escrow service has both, then giving party A the item and party B most of the cash, minus their fee.

It's about layers of abstraction. The Bitcoin architecture provides an abstract, lower-level interface for higher-level functionality to be built upon [1].

[1] http://en.wikipedia.org/wiki/Abstraction_layer