I think that statement may be a little broad in its reach. Not all condensers need phantom power. Let's say instead that all condenser mics require a charge across their diaphragm.
Some mics (electrets, for example) have a built in charge. Others (tube mics) may use a higher voltage directly from an outboard power supply, while still other mics use built-in batteries to supply the charging voltage.
But phantom power (44 to 52 Volts DC, across Pins 2 and 3) is a very popular form of powering a condenser mic, but it's not the only way.