I understand what you are saying, but this is a bit of a crooked reasoning in some cases.
Would I buy a book on performing surgery on the spine, read it over the weekend and perform an operation on Monday ==> absolutely not.
Would I read a book on investing, read it over the weekend, and place an order for EUR 1 mio on Monday ==> absolutely not. But Joe Average his investing portfolio is probably fairly limited (maybe EUR 5000?) to start with en thus it can make (more) sense to start trading on Monday while learning.