No, clients don't need to understand how RM advertising works. Thats not their expertise and its unreasonable to expect that.
All professionals, whether they are plumbers, lawyers, bankers or anything else, have to do business development. It sucks that BD is unpaid, because sometimes it can be more time consuming than actual engagements, and not every BD effort will turn into a paid engagement, but that is true across the board.
I don't know nor care how plumbers advertise, so I should not need to know nor care how you advertise.