So, in layman's terms: in level 10, for the most part, 10.0 is the highest score you can get. So, if your goal was to score well in level 10, once you have a 10.0 start value, you probably wouldn't compete extra skills that would only serve as risks and opportunities to get deductions. So you might have maybe 4-5 risky skills in a level 10 routine, and you might still have a 10.0 start value, so that's your routine. Simple as that. Why add extra skills that you don't need if you already have your 10.0 start value? Fewer skills means fewer opportunities for deductions.
However, in hopes and elite, there's no top out score. So the more difficulty and connection value you compete, the higher your start value. So you might compete 8-9 risky skills. Maybe more. You might still get deductions on those skills, but you also have added start value, so it's more worth the risk to add more and more risky skills in the elite world. So maybe your start value in hopes is a 14.9. You get deductions on several skills and still maybe end up with a 12.9. Not a bad score at an elite qualifier. Here's where it gets tricky: you might compete the exact same difficult routine in a level 10 meet to get competition experience with your Hopes routines. However, in level 10, you are at a 10.0 start value regardless of all the extra difficulty. You don't get extra credit. There's only debit from the 10.0. So, with the same deductions that you received at the hopes meet, but only starting with a maximum of 10.0 score, maybe you get an 8.0 even for a good routine. If you dropped some of the skills in your routine, you would also drop potential deductions. So competing maybe 3 fewer difficult skills at a level 10 meet might get you a point or more higher score simply because you had less for the judges to deduct from.
Clear as mud?
There's more to it than that, but maybe that explains a little bit of the difference?