I'd love to hear it from Dom Corner why the number of destination systems present on any given mission board is relatively low; it often feels like all say 30 missions on the board from 7 or 8 factions go to the same 5 or 6 locations, and all of them are within one jump for your average ship.
Only ship in my fleet with a sub 20LY range is the loan-winder, which doesn't technically count, cos I don't own it. Even in the FDL and Vette I can qualify for most mission destinations in a single jump and you're right, they're 'clumpy', but not in a way that suits my play style.
I figured hi-sec, hi-pop would be the busiest, but looking at the board it doesn't seem so. I see a lot to unexplored systems, which I'm not prepared to go to unless the ship I'm in has an ADS and DSS (OCD), and that assumes I want to put the time into scanning the entire system right now, then going far enough away to sell the data so I can't lose it.
When I am in that kind of mood however, or I need to pre-scan a lo-sec IF before starting the current CG, I'll take as big a delivery stack as possible, to any station or planet base in that system, since I've already committed myself to the (unknown) amount of time it's going to take to visit and scan every body before leaving. Sometimes I'll also take orbital and planetary salvage or scans, depending on legality, SRV and collector limpets fitted.
That activity is highly enjoyable, provided the hurry up wrinkles allow enough time to dawdle a bit here and there. It's really not that I don't enjoy doing the missions themselves, and that's what makes it worse.
I really like a lot of them, but I'd also like a lot more of them to integrate with my flight plans.