why do i need to transform, integral transforms?

Basically the integral transforms used to transfer the function from the time domain to frequency domain and vice versa. For example for those transform techniques, Laplcae Transform, Fourier transform, Z-transform, Poisson Transform, ...etc. However, why do i need to change back and forth from Time domain to Frequency domain and how can i judge the necessity for conversion??

Note:- I'm more concern about this topic from Electrical engineering perspective.

Looking Forward

Thank you in advance