Why are low wing planes not used as trainers, or seem to be more difficult to fly from what I have read here?
Is it just because you've got a few more inches of leway for a wobbly landing?

The high wing is easier to design with greater stability. Think of a pendulum and the weight being on the bottom (fuselage). Now try balancing a stick (not as easy). When landing if a wing is low it will catch the ground much easier in a plane that already has the wing on the bottom. There are quite a few planes that use low wings and do very well as second planes however including the Sig "star" series.

EXCAP232

Dittos to what Excap said. Additionally there is another reason probably just as important but somewhat overlooked and that is learning to maintain orientation in all attitudes and light/cloud conditions.

Learning this ability seems for most to be easier with with a high wing cabin type or parasol airplane with dihedral. Visually a low wing particularly without dihedral tends to be more difficult to maintain orientation with and thats not desireable for an initial training environment.

John

Dittos on all the above and this: High wing "trainer" type aircraft have what is called "self correcting or self righting tendencies". What this means is the plane is built to be inherently stable. They don't like to spin or fly upside down. If you get into trouble, just let go of the sticks and the plane will tend to right itself. Now this is just the start to a full recovery of a bad attitude and the plane isn't going to totally correct itself in every troubled situation. Otherwise we wouldn't need instructors, but the plane likes to fly stable and upright. Just like when you turn your car, after the turn the car wants to go back straight. When you turn trainers it's easy to come out of the turn because the plane wants to fly straight again (if it is built straight and in trim and if the wind is low). Low wing and most shoulder wing planes lack this self righting tendency. Basically they go where you point them and if you make a turn, you have to turn to get back where you started. It takes more work because you are flying the plane more, but it is more fun in the long run because you are not fighting the self correcting traits of the plane when you go to do wild stunts.