Good point. And that desire to learn/understand is something that's hard to teach. Some junior devs just grow dependent and are content to stay where they are.
When I was in college, I tutored CS. So, I hung out in the lab a lot and frequently helped people with programming assignments. I would always try to help them arrive at the answer vs. just giving it to them. With some people, this worked very well. They just needed a nudge or a little help framing the solution.
But, with others, I could spend literally hours trying to get them there with very little progress. In some cases, I finally had to all but give them the solution and help them code it. Thing is, many of them were OK with this.
So, after a time, when certain people asked a question, you kind of knew what you were in for.
What surprised me, however, is that in large enterprise settings, you had teammates who were similar. I don't know if you could get away with that in a startup environment, but some enterprises are large enough that they can just "carry" some team members.