Yeah...if you don't stress the body there's no reason for it to break homeostasis.
It wants to live in a happy bubble, drinking umbrella drinks by the pool, surrounded by beautiful people in tiny clothes.
Why go to the trouble if you don't have to?
It's the same reason most people stay skinny, fat, unhealthy, broke, etc.
If you can get by, as you are, why go beyond your comfort zone? It's easier to just complain about shit than put in work.
Everytime you lift, provided you've you've adequately stressed the muscle, your body will compensate. Yes.
Starting out, most gains will probably be more neurological though. As you ingrain movement pattern, you're body will become better at handling said movement's. You'll see the biggest strength jumps here.
Strength gains will taper over time as you become more advanced, and will depend more on programming and diet.
And, of course, recovery.
Bear in mind that muscle and strength don't necessarily increase proportionaly.
But there's really not a black and white answer to your question. No you don't progressively get bigger / stronger every time you lift. If it were that simple we'd all be walking around looking like Kai and pulling like Brian Shaw.