Why do people state their circuit uses  transistors?
Once upon a time, transistors were likely to be the most expensive part in a simple amplifier or oscillator design. Even today, a discrete transistor is likely to be 2 to 10 times as expensive as a discrete resistor or capacitor.

So a "one transistor" circuit was  roughly half as expensive to build as a "two transistor" circuit. And cost was an important reason to prefer circuits with fewer transistors.