Although most time-boxed meetings take the amount of weeks in a sprint into consideration, none of them seems to include the number of team members when calculating the max duration.What I mean by time-boxed meetings: Sprint Planning, Sprint Review, Daily Scrum, ... - not the sprint itself.Let's compare a team of 3 to one with 9 members.According to Scrum we have at max 15 minutes to all answer the '3 big questions' during daily scrum - no matter if we're 3 or 9 people.Same goes for the sprint review. 9 team members might produce triple the value that 3 do, but again we have 1 hour per week of sprint.What I would expect is something likemax duration of a sprint review = #ofWeeksInSprint * #ofTeamMembers * someHourConstant.Why does scrum ignore this factor? 
Why doesn't team size affect scrum time-boxing for meetings?
scrum
You're taking scrum to be a set of instructions you need to follow to the letter - and it's not meant to be. The time boxes are there to give you an idea on the typical situation. 9 developers in a standup may not work for the estimates they gave: if so, increase your timebox!The important part of the time box is to make people realize that there is an upper limit on how long they can go, keeping the filibusters to a minimum. Try it for a week and see if the amount of time you gave yourself is reasonable - if it's too long, shorten it, if you keep running out of breath to fit it in, make it longer. Remember, Individuals and interactions over processes and tools. If your process is keeping you from interacting better, change your process!