This reason is perhaps a bit more frivolous, but I was thinking about this lately. I think I'd have a hard time getting the kids to school on time with a minimum of fussing. My kids aren't morning people. They do wake up early because of the sun (and won't that be fun once it hits summer and it gets light around 3.00), but both of them like to go back to bed after Mass most mornings. I also find that I'm sometimes more rushed getting them out the door when we have to be somewhere at a certain time. Now, I know that if we were in a routine with it, that likely wouldn't be the case, since we're rarely rushed getting out the door for Mass. Obviously this isn't the foremost reason for me, but just something I was thinking about recently.
On a more serious note about time, though, home educating also means my children will have more time to devote to subjects they enjoy, or will have more time to master a concept. They won't be rushed with it and won't have to either move on before they're ready or lag behind waiting for others to catch up. They won't have to worry about the arbitrary schedules that the teacher must follow. They won't have to curtail their time to look at other subjects that are not subject to standardised testing (I'll not get into my rant on standardised testing right now other than to say that I think they're often a better test of how good a test-taker a person is and not a true measure of what they know; this isn't always true, but often, in my opinion).