'primarily serve' is a correct and usable part of a sentence in written English.
It is used to indicate that something is mainly used for a particular purpose or function. For example, "The role of teachers is to primarily serve as a source of knowledge and guidance for their students."
I also exclude short systems that primarily serve as transit within a business district.
In southernmost Westchester there are a number of grocers that primarily serve nearby enclaves of Indian expatriates.
The rifugi, or mountain huts, primarily serve hikers in summer with only a few open in winter.
The Yankees had already told Posada that he would primarily serve as the designated hitter next year.
Lennar proposes building a 900-foot-long bridge over Yosemite Slough that would primarily serve rapid transit.
In fishes, the ribs primarily serve to improve the leverage of the myomeres in producing the undulatory movements of swimming.
The fund makes investments on a competitive basis into financial institutions certified as C.D.F.I.'s that primarily serve economically distressed markets.
Instead, the White House has settled on an exemption that only covers religious institutions that primarily serve members of their own faith.
In Pittsburgh, where US Airways has already eliminated a third of its flights, the schedule will be adjusted to primarily serve local demand, it said yesterday, hinting that more cuts are in store.
Under its reorganization plan, ANC said it would close 179 of 531 Alamo Neighborhood outlets, which primarily serve insurance companies, and combine Alamo and National operations at 75 airports.
The answers he got led to an immediate architectural response: his Makoko Floating School, completed in March 2013, would primarily serve as a school and community centre, while also being scalable and adaptable for other purposes.
