Offering civil service will make the project economically wise, not to mention that it is also endangering national security if we depend on American GPS for civil positioning service.
China's investment on European Galileo system has got China nothing, Europeans basically shut China out of the project despite our huge investment in the project. Rumor says India gains more access to the project though it invests much less than China.
Beidou project is like another version of Chinese space station project. After China got denied the partnership in International Space Statiion, China has committed to build her own.