Why fsk does not used for high speed mode?

Frequency Shift Keying (FSK) is generally not used for high-speed data transmission because it requires a larger bandwidth compared to other modulation techniques like Phase Shift Keying (PSK) or Quadrature Amplitude Modulation (QAM). The inherent nature of FSK, which relies on shifting between discrete frequencies, can limit the data rate and increase susceptibility to noise and interference. Additionally, as data rates increase, the frequency separation needed for reliable detection may become impractical, leading to reduced efficiency and performance in high-speed applications.