That is problem. You sure could make tiny strip (10m x 250m), nearly everywhere, even at the center of old city.
But large planes need much larger strips, for example typical international airport have strip 30m x 1600m.
Why so much difference, because economy. It is much more effective to make large strips in large cities (or near them), than to make off-road planes (google Bush plane) which will have much more expensive cost to transport weight-kilometer or passenger-kilometer.
From where become expensiveness. Well, most effective planes flight fast at high atmosphere (because speed of sound is significantly higher in low pressure), but they also have high landing speed, and unfortunately, brakes (very similar to automobile) need to dissipate all energy from speed, calculated from simple formula (m*v^2)/2, so with double speed have quadruple energy.
Energy dissipation from plane brakes is really big problem, so big that nearly all big planes have special "thermo-accumulating" weights inside landing gear, which considered to heat fast when braking and then few hours dissipate heat. Extreme example was Concord, on which brakes cooling about 11 hours after landing. Bush planes are slow, so they don't have this problem.
Second problem, because of engineering considerations (physics), large planes usually are tall, but not too wide inside, and very big loads are just considered to transport in "horseman" configuration, mean load placed on top of plane, so need special crane to load/unload.
But large planes need much larger strips, for example typical international airport have strip 30m x 1600m.
Why so much difference, because economy. It is much more effective to make large strips in large cities (or near them), than to make off-road planes (google Bush plane) which will have much more expensive cost to transport weight-kilometer or passenger-kilometer.
From where become expensiveness. Well, most effective planes flight fast at high atmosphere (because speed of sound is significantly higher in low pressure), but they also have high landing speed, and unfortunately, brakes (very similar to automobile) need to dissipate all energy from speed, calculated from simple formula (m*v^2)/2, so with double speed have quadruple energy.
Energy dissipation from plane brakes is really big problem, so big that nearly all big planes have special "thermo-accumulating" weights inside landing gear, which considered to heat fast when braking and then few hours dissipate heat. Extreme example was Concord, on which brakes cooling about 11 hours after landing. Bush planes are slow, so they don't have this problem.
Second problem, because of engineering considerations (physics), large planes usually are tall, but not too wide inside, and very big loads are just considered to transport in "horseman" configuration, mean load placed on top of plane, so need special crane to load/unload.