Why the title exists
Roofing, siding and remodeling companies sell through the free estimate. The person who shows up to give it gets called the estimator, even when the visit is a full sales presentation. Some companies choose the title on purpose, because 'sales rep' can put homeowners on guard.
In a 2017 sample of contractors, the split between Sales Representative, Project Manager and Estimator titles was 80% / 7% / 3%. Owners described a 'stigma attached to the title' of salesperson, which is part of why softer titles stick.