> notebooks are hard to sterilize
Washing / sterilizing the lab coat has the same effect as erasing the data written on it.There isn't a library of lab coats which contain notes written on them, for future consultation.
A notepad page is also easier to permanently sterilize (via incineration) than a lab coat.
I think it's pretty clear they were taking ephemeral notes, not using them for long-term archiving.