Why do all models have to be tall? Why don’t we see many shorter models?
Well, visually, the main reason models needed to be tall is that they should appear to fit the clothing better. The idea basically is that the clothing will hang nicely on the tall individual, as if on a hanger. If an individual modeling the clothing is short, the clothing will bunch up and wrinkle, not looking as smooth and flowy as desire by most designers. This is the reason why mannequins are generally tall.
The other reason is a matter of displayed confidence. At first glance, being tall is a symbol of confidence and attraction.
The model may look really confident and attractive if they are tall and the clothing may look better as it also displays well on a taller model. There are always exceptions however. If you wish to be a model and are not tall, there are fields of modeling that do not require tall height. Fitness models, lingerie models, and bikini models are just a few examples of modeling fields where a shorter person may pursue.