Yes, I do think people are medicated to keep them quiet - particularly on a ward where the nurses want to create a calm atmosphere for everyone, and also are far too busy and understaffed to have time to spend with people. Also the waiting lists etc. for therapy are really long, and therapy takes time to work. It is unfortunate but probably reality.
How long ago was your quetiapine increased? It may take some time to get used to the increase. When I was first put on olanzapine I was completely knocked out (missed out a whole day - woke up and thought it was the next morning when in fact it was two days later!) but when I got over that I was on up to 40mg a day when the maximum dose was 20mg (I think). And I was on a ward where they got you up at 7.15am and didn't let you go to your bedroom or for bath or anything until at least 9.30pm (sometimes closer to midnight if there were a lot of showers to supervise), and you weren't allowed to sleep in the day. I was quite tired but not excessively. So maybe things will get easier if you stick with it. It is HORRIBLE being over sedated though.
I agree with pp that you need to discuss with your CPN or psychiatrist. Ask them why it has been increased (if you don't know) and if there is any chance of reducing it. Or, if you are not tolerating it, then changing. I think aripriprizole is meant to be the least sedating, but they may not want you on it as it is not very strong either.
Are there other steps you can take to manage your mental health so you are in a position to reduce? Showing them that you are able to manage yourself if you see what I mean. Positive self-care, mindfulness, exercise, therapy, holistic stuff and all that jazz.
I really wouldn't decrease without medical advice though. I did that and it did not end well. You obviously don't want to end up back in hospital because it's pretty rubbish.
Take care and I hope you feel better soon.