This is particularly required in the case of welding transformers, where high currents may occur if the welding electrode gets fused with the job. Thus these transformers have high leakage inductance.
Leakage Transformers are also used in extra low voltage applications where short circuit conditions are expected. The primary and secondary windings of a leakage transformers are adequately sized to withstand heavy currents in short circuit conditions.
Leakage Transformers are also known as Stray field Transformers.