Reserving a specific pitch

I know I'm not qualified to comment really being a new member but I do feel a little penalised for working for a living, basically because even though I can book weeks in advance, when I arrive on the first nght in the evening effectively you are left with the pickings of what everyone doesn't want. Why can't you book in advance and reserve "Pitch 20" for example? I'm just heading off to the USA in a Motorhome and every site we've booked we already know exactly the pitch where we will be based.

Thanks in advance.