Wild guess from the highly relevant experience of having played Kerbal Space Program: if you don't actually intend to achieve orbit (which is mostly about going

Wild guess from the highly relevant experience of having played Kerbal Space Program: if you don't actually intend to achieve orbit (which is mostly about going sideways really fast, not up) it may be more fuel-efficient to reach your target by going relatively high, to lengthen the amount of time you spend in little/no atmosphere before coming back down. Or maybe you want to be going really fast on the way down for some reason. Or (relatedly) it's harder to shoot down a missile on that kind of trajectory than a flatter one.