The plain Magnet is mostly a crafting component. The real quality-of-life upgrade players usually want is the Infused Magnet made from that line.
Keep Magnets for recipes involving magnetic or pickup-related utility items. They are a stepping stone instead of the final tool.
If you carry an Infused Magnet anywhere in your inventory and hold shift, it pulls nearby dropped items toward you. This makes it much easier to gather loot while mining, chopping trees, farming, or cleaning up mob drops.