Hmmm, I am no expert, so don't take what I will write to heart.
My theories....
Maduro wrappers are a thicker leaf as compared to most natural wrappers. I suspect when the wrapper is applied, the maduro leaf has more tensile strength, and can be wrapped more tightly around the binder and bunch where in contrast the thinner natural wrappers are more fragile and need more delicacy to be applied, thus a bit looser in construction.
Another reason for a tighter draw might also have to do to how much moisture can be absorbed into the leaves. The maduro, being thick, has the potential to retain more moisture and slightly expand (swell up) more so than the thinner natural wrapper.
Of course I am just really blowing a lot of smoke and you are probably smoking sticks that are plugged or the humidity is too high in the maduros you smoked. The only "maduro" I had draw problems with was the El Mejor Expresso churchill.