Smaller planes tend to be twitchy compared to larger planes. Things happen faster as well, so you go from OK to tip-stall or inverted faster with a smaller plane. They also tend to be affected by wind gusts more than larger planes.

And since the plane is smaller, it's a bit harder to see when flown farther out. So it's natural to fly it closer in. But the stall speed isn't much slower (if any slower at all) than a larger plane, so you go from "too far away" to over the runway faster, leaving you less time to figure out your landing approach.

All this is really general. There are exceptions. A lot of this is actually due to the fact that the "standard" .25-.30 size plane is really smaller than it should be, and has a wingloading that is higher than it needs to be.