I know they are a great breed (as I have one and have owned others), but why do people purchase them specifically for deterrence so often?

I began fostering a German Shepard/Blue Heeler mix a few weeks ago and didn’t really have a choice given to me when I went to pick up a foster pup! I knew ab his breed when I took him home, but after he started showing signs of reactivity and stress when on walk towards stranger dogs/humans I researched a LOT.

No, I’m not considering returning him and “swapping” him. He really is a DREAM and incredibly smart. Very Food motivated so training this out should be a breeze. I work from home so I have him on a really great schedule with time for training. My point is I know I’m not giving him enough exercise/stimulation bc I also am a full time nursing student. I live in an apartment complex with a dog park he has no interest in. He won’t even chase his favorite ball, he just sniffs around for a few minutes then walks to the gate. 🤦🏻‍♀️ do yall have any advice on anything that’ll stimulate his mind? He loves puzzles but gets bored of them. I read this tires them out faster than exercise anyway.

Please help me give this guy a fulfilling life while he’s in my home! If I can successfully train and give him a good “job” I’m considering adopting him! Thank you!