brent It's safe to say no business ever bought a single copy. just one copy and multiple licences I assume. A small shop like a florist, for example, might have 1-2 computers, but a large taxi dispatch company might have 50. Mid-sized companies and corporations had to be the revenue backbone of Enterprise.
I don't think that Enterprise was ever marketed to midsize businesses. I headed up IT for an Enterprise customer 1995-2000 (about 2,800 seats, 50 dedicated IT staff). We were considered to be at the lower end of the Enterprise market during that period, as I recall.
I don't know how Microsoft defines the lower limit of eligibility for Enterprise licensing at this point, but Microsoft now says "The Microsoft Enterprise Agreement offers the best value to organizations with 500 or more users or devices that want a manageable volume licensing program that gives them the flexibility to buy cloud services and software licenses under one agreement." That sounds about right given the nature of Windows Enterprise and the tools that it offers over and above the tools offered by Windows Pro.
The thing to keep in mind is that Windows is Windows is Windows, as far as user interface is concerned. Home, Pro and Enterprise are more or less identical in that respect. The difference between the editions are security and management tools.