It amazes me how some people still don't get the "book now, plan (cancel) later". One guy told me he was trying to figure out first where to stay & by that time he missed it.
Problem with people booking 5 itineraries in such a case, is when flights "artificially" sell out, and then there's only flights with 2 stops for the dates you want etc. Then all those people booking multiple itineraries, or people booking when they're 95% sure they can't go, or just in case, or even just to feel like they were able to snag a good deal, cancel their itineraries, leaving the person who actually needed those dates, with the weaker option, because he wasn't as quick as those just randomly booking.
Not saying people shouldn't book if they have half of chance of going. But to grab multiple dates when you know you're only going to use one of them, tops, can be unfair.