Sanitation is important on the cold side of the process, ie after you start chilling the wort. During the boil, the heat keeps everything sanitized.
You obviously don't want stuff falling into your brew kettle, but sanitation isn't an issue until after the boil is complete.
For me the switch to outdoors was due to full boils, larger batches, and not smelling up the house with hop smells. (it did not bother me, but the wife and kids did not like the smell)