Yes, these kinds of dream students are fantastic. However, in my experience, they're a relatively small percentage of any given class.
Off the top of my head, I'd say something like only 5% of my students at any one time are like that. If you included students who are still good students, but are primarily focusing on getting good grades, then the number goes up to maybe 40%.
Then there's the ones who are putting in a mediocre effort - those make up the bulk of any class. Finally, you've always got several who are the complete opposite of your SRL. You're not really sure why they enroll, because they clearly not there to learn.
I primarily teach adult learners, so even my most dedicated students still have to focus on other real life issues with sick kids, job schedules, etc. It's not that they don't value learning English, but there are times when you just have to skip class to take the kid to the ER, attend parent teacher conferences, work overtime, show up for court hearings, renew visas, attend funerals, return to home country, etc.