Hollow Metal doors and frames get specified in many commercial and industrial buildings (probably because the steel holds up better than wood).
In recent years, I've been using hollow metal frames with pre-finished wood doors in many buildings. The hollow metal frames provides a durable way to complete the gypsum board openings and the pre-finished wood doors are attractive and economical. The Mohawk Doors seem to be common. Wood frames, using wood trim boards around a wood jamb and header, are also popular. Wood frames tend to be site built, except for pre-hung wood doors. Aluminum and glass storefront also gets used often in commercial buildings.