I think the idea behind using LinkedIn suits professional B2B services in a far more cohesive way than Facebook or Twitter can. In essence, you need to account for the types of content published on each platform. Facebook is fantastic from the perspective of reach, especially as promoted posts are impressions based, but my opinion would have me say that the types of content on Facebook, and the types of content that people look for on Facebook is fairly informal in tone. Perhaps not quite so much as Twitter, but I still think that business decision makers may not explore Facebook looking for solutions.
The very nature of LinkedIn allows you to discuss, in detail, relevant content with others in business. It also allows you to talk shop and network with others, so even if posts may not generate business leads, you can further your professional knowledge and increase your business scope.
I wouldn't even say that using Facebook is 'easier', just that it is the primary solution nowadays for increasing the volume of reach.