No, you are not the only one, but Fanduel's lineup entry format makes it difficult for us to do that. It might not be too difficult if you only ran 1 lineup, but for the people who run many, it would be hell to set up. Draftkings format makes it easy, if you enter a dummy lineup that takes a bunch of entries, you can simply upload the new lineups, and then merge the old dummy lineup into the new one (manually). I'm not saying you should play draftkings (because I still prefer fanduel but that's not relevant), just saying it's not as simple as one may think.
I understand that you may want to reserve your spot in many tournaments but perhaps it might be safer for you to not build dummy lineups, pressuring you to play even if you don't have time to really dedicate your lineup. Most tournaments don't fill up until the last hour or so, so as long you build the line up prior to that using lineup cruncher it might work out. I'm just saying it might end up saving you those times where you enter a dummy lineup and find that you didn't have time to actually make a lineup. This happens a lot if you live on the west coast...
Anyway, maybe I'm wrong about it being difficult, and Dave (praise upon him) will figure out a way for it to do what you want, because ideally, it should be able to do that. But I'm not sure if it's all that easy to do.