I started my professional career in the advertising space. Digital marketing was beginning to become part of the standard print and television packages that would make an "ad campaign". I can still remember learning specs for display ads and constructing briefs for creatives. Countless hours spent.
Fast forward three years working in a small digital agency creating websites and display campaigns. I was no longer creating specs but laying out assets. Three traditional display sizes, painstakingly reviewed with the advertiser to get image, color, and spacing just right. Countless hours spent.
Fast forward 8 years and software can now generate 20+ ad sizes for responsive layouts and mobile serving in a matter of minutes. Love this industry!