This form of transportation is very much connected to the culture and environment. For instance, Ghanaians value time differently than Americans do. In the U.S., many people believe time is money and things must run on a schedule. Here, people think time is just time and there is no need to rush anywhere. I have experienced events starting 30 minutes after the scheduled time. Similarly, tro-tros don't run on any kind of schedule so it's hard to plan a journey. This does not seem to bother Ghanaians since they are largely not in any rush.
As for the environment, the average daily minimum wage here is about 10 cedis, or $2. This makes owning a car and paying for gas cost-prohibitive for the common person who also has to support a family. A tro-tro ride costs less than a liter of gas, so it is an affordable option for the people of Ghana. In addition to affordability, this form of transportation provides jobs for the driver, mate and people selling goods alongside the roads. Tro-tros are a necessary part of people’s lives who depend on them for transportation and work.
