Why is it important to keep lead lengths short for components used in circuits for VHF and above?

Every physical length of wire, including the small leads attached to resistors, capacitors, and transistors, possesses a tiny amount of inherent or parasitic inductance. At DC or low audio frequencies, this tiny inductance is completely negligible. However, inductive reactance increases proportionally with frequency (X_L = 2πfL). At VHF and microwave frequencies, even a fraction of an inch of component lead can introduce enough unwanted inductive reactance to drastically alter the circuit's intended behavior. If leads are left too long, this extra reactance can cause tuned circuits to detune, create impedance mismatches, or even induce destructive parasitic oscillations. Keeping leads as short as possible ensures the circuit operates strictly according to the intentional component values.