In a free market system, if nobody thinks something is worth supporting financially, then it isn't worth supporting financially, and doing it for free distorts the economy and reduces efficiency.
It doesn’t reduce efficiency because the volunteers are the judge of worth and their’s is the only opinion that matters. The cost of providing services can be quite low when the labor is volunteered, so the cost to benefit tilts heavily in the direction of net benefit, i.e. efficiency in producing positive outcomes at a particular cost.
> doing it for free distorts the economy
It's very noble of you to do stuff for "the economy". Most just pursue selfish needs and desires like food, clothing, shelter, and wanting to make a difference in others' lives.
It seems we have different ways of looking at the world.