Translation:The dogs run because the man is calling them.
I don't know if it's a fact that גבר is used more than איש. If it's a fact, there could be other explanations. They stress different aspects, so in many contexts one of them is more handy than the other. Both have other meanings. איש to mean "husband" is quite rare, and I think almost never ambiguous with non-husband "man".
In other discussions it was mentioned that "read to" is more commonly מקריא in modern Hebrew. It was mentioned that קורא ל is still used in this sense; but I'll add that this is so mainly if the thing being read is specified, e.g. קורא לילד ספר. For me it seems very stretched to interpret קורא להם (period) as "read to them".