Maybe your lawn service is not bagging the cut grass or maybe their
equipment is not picking it up very well. If they are using mulching type
mowers it's possible that it's not cutting it up fine enough.
We had a Troy Built mulching mower that did an excellent job of mulching but
when we replaced it with a Craftsman mulcher it did a sorry job so had to go
back to bagging, in other words, all mulchers ain't equal. RM ~

PS, The new Troy Built mowers are not half the mower the old ones were,
which is the reason we changed.