To work with architectural units (inches and feet), it is necessary to set architectural units in several places:
1 - in the Units dialog - Length type and Insertion scale,
2 - in the Dimstyle dialog for current dimension style on Primary units, Alternate units tabs,
3 - in the Scalelistedit dialog: click the Reset button, then choose Imperial scales,
4 - in the Design settings dialog: Main options tab - Design - List of drawing scales - Document only or All.
To apply all these settings for all new documents, save an empty drawing with these settings as a dwt file and use this file as the default template in Options - Template usage - For new documents - Default template file name.