Why is not tram popular in most countries? This list suggests that tram systems are massively unpopular in most of the countries outside the Western sphere.

Why is not tram popular in most countries?
My guess: high investment costs, low gains relative to alternatives such as buses. You need rails and electric lines, which are expensive. In the western hemisphere trams already existed before alternatives such as large buses came about, so the costs consist mainly of maintenance. In other parts of the world the infrastructure is not in place, and getting it is expensive. For buses the infrastructure is already there as all you need is a decent road.