There are always discontents and issues that will motivate protest. What varies is the resources available to them, and that they can mobilise. Even if grievances didn't exist a good Social Movement Organisation (SMO) would be able to convince people otherwise, so they don't even figure as factors.

Wealthier societies have more social movements because they have more disposable resources (including money, time, better education, means of communication and transportation, and so on)

The character of a movement is shaped by the mobilisation and management of resources (e.g. a SMO that has huge resource demands will most likely be more hierarchical).

Likewise organisation choices driven by other choices (e.g. the green preference for decentralisation) may determine the resource mobilisation capabilities of an SMO.

SMOs may often compete for resources, especially if we consider activists to be resources. Thus considerable energy may be diverted into competitive activities that don't directly impact on their goals.

Movement "entrepeneurs" have an important role in leading mobilisation efforts
Appropriate and effictive resource mobilisation can determine an SMO's success