If every door in your home uses the same simple lock type, once someone figures out or copies one key (or picks one mechanism), the rest become easier targets. Using a combination of lock types—say, a main deadbolt plus a latch on the primary door, and simpler locks on inner doors—creates multiple hurdles.
The main entrance should ideally have the most robust system: a good-quality main lock, maybe a separate chain or bar, possibly a second deadbolt. Secondary doors, like balcony grills or back doors, can also have different styles—padlocks, sliding bolts, internal latches.
The idea is to make forced entry time-consuming and noisy. Each extra layer increases the effort and risk for someone trying their luck. It’s not about becoming a fortress, just about not being the easiest option on the street.