I used to work in the community, visiting patients at home. The team consisted (still does but I am now retired) of OT's, Physios, Nurses and our support staff We wore our uniforms from house to house (some pretty grotty houses) and sometimes we also did special assessments like taking someone to the local supermarket to see how best to suggest that they manage shopping etcetera. While we would do our best to avoid the worst of the dirt in the dirtiest houses, we had an extremely low rate of cross infection from wound to wound and of carriage of things like Noro.
This was, in the opinion of our local infection control team, because we were obsessive about hand washing and use of gel hand cleansers. The "bare to the elbow" rule is to facilitate handwashing because if you don't bare wrists and above, you won't be inclined to give the hands a good wash. We also actively discouraged the heros and heroines who struggle to work with colds and stomach upsets and generously shared the bugs around.
The other advantage that home care has over hospitals is that at home you are likely to have been in contact with all the bugs that you will meet in that environment and your own natural defences will largely be adequate to deal with them, even if your immune system is somewhat below par. In hospitals, you meet new infection challenges from other people. Its basically the same reason that children get lots of buggy things when they first start school or playgroup and again young adults do when they go off to college or first job.
The other proven, IIRC, infection risk is from rings because they harbour dead skin cells and so on.