[Spisivavona]

Bismillah
The purpose is not to choose a school of thought but to follow tried and tested method. It is not about following some ism!! It is more about following tried and tested codified method that stood the test of time.

One chooses school primarily based on the material/resources available to them i.e ease of access to scholars and materials.
Secondly it is based on the dominant schools in the area where most people gravitate towards one school. this makes life easier.
Thirdly ones lifes circumstance.
Fourthly personal inclination.

The tow most developed schools are Hanafi and Malaki school as they have huge amount of materials and experience dealing in non muslim setting. This is a view of Shaikh Nuh Ham Meem Keller (a shafi scholar).

Allahualam