I’ve noticed that the LM317 linear voltage regulator is still widely used in various hobbyist and even some professional circuits, despite the availability of efficient and compact switching regulators. Considering that switching regulators offer better efficiency, less heat dissipation, and smaller footprints, what are the reasons engineers or designers still opt for LM317 in certain designs? Is it due to simplicity, cost, noise sensitivity, or something else?

Yes, much of the heating behaviour is inherent to older bipolar-driver ICs like the L293D and L298N. Those chips use bipolar transistors (Darlington or bipolar output stages) with large voltage drops, so a significant fraction of motor power is dissipated in the chip as heat. Wiring and supply issues (thin wires, poor decoupling, undervoltage, high stall currents) can worsen the problem, but replacing the driver with a Modern MOSFET-based H-bridge or dedicated MOSFET motor driver typically reduces losses by Orders of magnitude and greatly lowers heat.