Some might argue that firefighters, career and volunteer, perform selfless acts of service every day just by performing the duties required in their departments' fire and emergency services mission.
Many departments have also instituted formal programs to engage with their communities under non-emergency conditions. There are many obvious benefits to these formal programs, including opportunities to provide fire- and life-safety education, become familiar with buildings in your response area, helping residents understand your department's capabilities and limitations, and just by fomenting overall goodwill.
Firefighters, of course, as this story demonstrates, are also well-known for simply being good neighbors. It's hard to estimate the impact of these random acts of kindness, but it seems likely they have something to do with firefighters' relatively high ratings of community trust.
These informal contacts with our residents are vitally important, and who knows how many occur each year.
Believe it or not, however, I've actually experienced situations where well-meaning firefighters received complaints for taking actions like shoveling a driveway, mowing a lawn, carrying somebody's groceries, etc.
I certainly don't think the risk of getting a complaint outweighs the benefits of doing the neighborly thing when it's appropriate and doesn't result in service degradation for the balance of the community.
At the same time, it's important to know your department's and/or jurisdiction's policies on providing informal service to residents, businesses and visitors.