Chef was released in 2009, which is relatively a long time ago for software. Since then it has been through several versions and many bug fixes and tests. All of this can make Chef more appealing to teams who are looking for stability and maturity, which are things that Chef brings on the table.
Pro Large community
Chef has a relatively large community. One of the reasons for it is the fact that it's a pretty old and mature tool. Chef, originally released in 2009, is a more mature product. Being popular and with a large and dedicated community means that Chef has lots and lots of resources and guides from third party sources out there for beginners to pick up. Not only that, there are also many plugins and configuration recipes made by the community.