Many modelers take their time when deciding which scale to model and the decision takes consideration of many things, not the least of which is personal desires.
For instance, if you are planning a railroad layout is your main concern running train operations (shipping and receiving) or depicting a particular era? Do you have access to ample space, or are you talking half a room for a layout? Will your eyesight allow detailing a five-inch railroad engine or would you be more comfortable with an engine that exceeds two feet in length?
It often depends on the type of scale modelling you do. Those who create static models like wooden ships or plastic planes often alternate between favourite scales to gain a different perspective. Those who model railroads in a layout stick to one scale.
If there is only one kit of the subject they are looking for, then that is the model they will build. Usually, large scale models have the best detail, but the variety of subjects is limited.
The biggest variety is found in 1/72 scale and these have adequate detail. It corresponds to one sixth of an inch equalling one foot making a six-foot man an inch tall. It is very popular among railroad modelers offering a wide enough selection to allow exclusivity for modelers who want to have all aircraft types represented in the same scale.
Wikipedia lists 76 different scales used in modelling ranging from the tiny 1:20,000 (used to depict a very large Zentradi spacecraft from the science fiction anime series Macross) to the large 1:3 (used for articulated dolls with ball and socket joints.
Most scale choice decisions are driven more by the modeller’s constraints rather than what is available. Factors such as display area work area and vision capability form the basis for the final decision.