I'll hold my hands up as guilty trying to learn crossovers before being able to properly hold an outside edge. But I've definitely recognised I've tried to take a short cut - borne purely out of frustration at having to slow down on corners.
Outside edges are my current nemesis, as said by Leif its really hard to learn the balance as you don't use your inside leg to count balance but you use your outer leg instead. Its something seemingly so simple, but really hard to get to grips with!
I try to do those figure of 8s, inside edges really easy, outside edges are a wobbly mess and half the time I aren't even properly on the outside edge as I wobble out of it. Its tricky.
(1) Edges (especially deep edges) are intrinsically easier to learn for inside rather than outside. If you are leaning inside, and your edge starts to slip, you can simply place your free foot on the ice, and it will save you from a fall. But, if you are leaning outside, and your edge starts to slip, you don't have that safety net ... you probably will fall.
(2) If you continue to have problems with your outside edges, have a coach or skate tech check your feet and skates. If you over-pronate, you will have great difficulty getting on to an outside edge unless you provide correction in your gear: (a) a corrective footbed, (b) moving the blade to the inside, or (c) shimming the blade on the outside (in some cases, a combination of two or all three of the corrections is needed).