That's....exactly what the HOA does though in this case - it vets said companies and pays them, through the HOA dues paid by Homeowners. Homeowners typically elect folk(s) to the Board who then make those decisions. That person usually lives in the neighborhood (at least in HOA's I'm familiar with) so they've got a vested interest in keeping things 'their best'

It's like a mini government, for the neighborhood. Then they contract out work that needs to be done to care for the things they cover (like the common property/green areas, pools, etc.), review/revise rules as times change, resolve HOA-rule-related disputes, etc.