Time to first solo also depends on how many exercises/skills your school thinks you need to master doesn't it? In my case it was not just circuits but also comms. failure, finding alternates, EFATO, FLWOP, stalling, go-arounds and when to go around as well as 3 landing configs. (glide, flapless and short field). Nobody could learn/master all that in under 10 hours I think. The authorizing instructor quizzed me for 20 minutes as to what I would do if the field was closed due to an accident etc. etc. The actual first solo circuit was such a non-event that I barely remember it. First solo X-country was when "it" really hit me.
Cheers