Why are DIP through-hole package ICs not typically used at UHF and higher frequencies?

At Ultra High Frequencies (UHF) and above, the physical dimensions of electronic components become critical. DIP (Dual In-line Package) components have relatively long internal bonding wires and external metal pins used for through-hole mounting. In RF circuits, these long leads behave like small inductors and tiny antennas, introducing excessive parasitic inductance and capacitance. This stray reactance completely changes the tuning and impedance of the circuit at high frequencies, causing signal loss, reflections, or unwanted oscillations. Surface-mount components are used instead at these high frequencies precisely because they eliminate this excessive lead length, keeping parasitic reactances to an absolute minimum.