The 40V maximum input voltage lets this regulator work directly off unregulated rectified AC rails (e.g. 24VAC rectified to ~34V) or 24V industrial buses without a pre-regulator. That saves a DC-DC stage and its inductor, but the 100mA output limit means the load must be kept light — think op-amp supply, small relay, or MCU I/O pull-up rail. The 5.5 mA quiescent current is typical for a three-terminal regulator of this era; it's not a low-Iq part for battery gear.
PSRR at line frequency — ripple rejection matters here
PSRR is 38 dB at 120 Hz — the standard ripple frequency after a full-wave bridge rectifier. That's adequate for general-purpose logic or relay supplies, but if you're feeding an audio stage or a precision ADC reference, the ripple rejection may be marginal. For those cases, a post-filter or a regulator with higher PSRR (like the LD39020 series) is worth evaluating.
Protection set and package
Built-in over-current, over-temperature, and short-circuit protection are standard for the L78Lxx family — the regulator folds back safely under fault without external clamp diodes.