RF and microwave engineers use different components (e.g., MOSFETs rather than GaAsFETs), and RF engineering has a number of unique applications such as RF heating (plasma), medical imaging (MRI), HF radar, and RF ID.
However, many techniques (power amplifiers, low-noise receivers, couplers, signal synthesis) are analogous and wireless communication is a major application for both.
Equally important is the attitude that the application of theory has to be tempered by practical limits imposed by stray capacitance and lead inductances.
The interests of microwave and RF engineers thus have much in common.